Suchergebnisse

The hydrogen evolution reaction (HER) is a key process in electrochemical water splitting. To lower the cost and environmental impact of this process, it is highly motivated to develop electrocatalysts with low or no content of noble metals. Here, we report on an ingenious synthesis of hybrid PtxNi1-x electrocatalysts in the form of a nanoparticle-nanonetwork structure with very low noble metal content. The structure possesses important features such as good electrical conductivity, high surface area, strong interlinking, and substrate adhesion, which render an excellent HER activity. Specifically, the best performing Pt0.05Ni0.95 sample demonstrates a Tafel slope of 30 mV dec-1 in 0.5 M H2SO4 and an overpotential of 20 mV at a current density of 10 mA cm-2 with high stability. The impressive catalytic performance is further rationalized in a theoretical study, which provides insight into the mechanism on how such small platinum content can allow for close-to-optimal adsorption energies for hydrogen. ; Funding Agencies|Vetenskapsraodet [2017-04862, 2017-04380]; Energimyndigheten [45419-1, 50779-1]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO Mat LiU) [2009 00971]

The chelating gadolinium-complex is routinely used as magnetic resonance imaging (MRI) -contrast enhancer. However, several safety issues have recently been reported by FDA and PRAC. There is an urgent need for the next generation of safer MRI-contrast enhancers, with improved local contrast and targeting capabilities. Cerium oxide nanoparticles (CeNPs) are designed with fractions of up to 50% gadolinium to utilize the superior MRI-contrast properties of gadolinium. CeNPs are well-tolerated in vivo and have redox properties making them suitable for biomedical applications, for example scavenging purposes on the tissue-and cellular level and during tumor treatment to reduce in vivo inflammatory processes. Our near edge X-ray absorption fine structure (NEXAFS) studies show that implementation of gadolinium changes the initial co-existence of oxidation states Ce3+ and Ce4+ of cerium, thereby affecting the scavenging properties of the nanoparticles. Based on ab initio electronic structure calculations, we describe the most prominent spectral features for the respective oxidation states. The as-prepared gadolinium-implemented CeNPs are 3-5 nm in size, have r(1)-relaxivities between 7-13 mM(-1) s(-1) and show clear antioxidative properties, all of which means they are promising theranostic agents for use in future biomedical applications. ; Funding Agencies|Swedish Research Council [621-2013-5357]; Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linkoping University (Faculty Grant SFO-Mat-LiU) [2009-00971]; Knut and Alice Wallenberg Foundation [2012.0083 CTS 15:507]; Centre in Nano Science and Nano technology at LiTH (CeNano) at Linkoping University; CoTXS; Ministry of Education and Science of the Russian Federation [14.Y26.31.0005, K2-2017-080, 211]

Multicomponent (TiNbZrTa)Nx films were deposited on Si(100) substrates at room temperature using magnetron sputtering with a nitrogen flow ratio fN [fN = N2/(Ar + N2)], which was varied from 0 to 30.8%. The nitrogen content in the films varied between 0 and 45.2 at.%, i.e., x = 0 to 0.83. The microstructure was characterized by X-ray diffraction and electron microscopy. The metallic TiNbZrTa film comprised a dominant bcc solid-solution phase, whereas a single NaCl-type face-centred cubic structure was observed in all nitrogen-containing films (TiNbZrTa)Nx. The mechanical, electrical, and electrochemical properties of these films varied with nitrogen content. The maximum hardness was achieved at 22.1 ± 0.3 GPa when N = 43.0 at.%. The resistivities increased from 95 to 424 μΩcm with increasing nitrogen content. A detailed study of the variation of morphology and chemical bonding with nitrogen content was performed and the corrosion resistance of the TiNbZrTa nitride films was explored in 0.1 M H2SO4. While all the films had excellent corrosion resistances at potentials up to 2.0 V vs. Ag/AgCl, the metallic film and the films with low nitrogen contents (x < 0.60) exhibited an almost stable current plateau up to 4.0 V vs. Ag/AgCl. For the films with higher nitrogen contents (x ≥ 0.68), the current plateau was retained up to 2.0 V vs. Ag/AgCl, above which a higher nitrogen content resulted in a higher current. The decrease in the corrosion resistance at these high potentials indicate the presence of a potential-dependent activation effect resulting in an increased oxidation rate of the nitrides (present under the passive oxide film) yielding a release of nitrogen from the films. TEM results indicate that the oxide layer formed after this corrosion measurement was thick and porous for the film with x = 0.76, in very good agreement with the increased corrosion rate for this film. The results demonstrate that an increased nitrogen content in (TiNbZrTa)Nx system improves their mechanical properties with retained high corrosion resistance at potentials up to 2.0 V vs. Ag/AgCl in 0.1 M H2SO4. At even higher potentials, however, the corrosion resistance decreases with increasing nitrogen concentration for films with sufficiently high nitrogen contents (i.e. x ≥ 0.68). ; Funding agencies: VINNOVA Competence Centre FunMat-II (grant no. 2016-05156), The Swedish Government Strategic Research Area in Materials Science on Functional Materials at Linköping University (Faculty Grant SFO-Mat-LiU No. 2009 00971), M – ERA.net (project MC2 grant no. 2013-02355), The Knut and Alice Wallenberg Foundation through the Wallenberg Academy Fellows program (P.E.) and the Electron Microscopy Laboratory at Linköping University, The Swedish Research Council VR Grant 2018-03957, The VINNOVA Grant 2018-04290, The Åforsk Foundation Grant 16-359, Carl Tryggers Stiftelse contract CTS 17:166, VR-RFI (contracts #821-2012-5144 & #2017-00646_9), The Swedish Foundation for Strategic Research (SSF, contract RIF14-0053)

Hinter Migrationsprozessen wird sehr viel schneller als hinter anderen historischen Vorgängen das Schicksal des Einzelnen greifbar. Für dessen und gegebenenfalls auch seines Herkunftslandes Interessen wird nicht selten Partei ergriffen, obwohl Forschung dem Anspruch nach werturteilsfrei sein sollte. Nicht zuletzt in Folge der "Flüchtlingskrise" von 2015 hat sich demgegenüber ein spürbares Bedürfnis nach wirtschaftswissenschaftlich und wirtschaftshistorisch fundiertem Orientierungswissen entwickelt, das die historische Migrationsforschung bisher nicht zu befriedigen vermochte. Anliegen des vorliegenden ersten Bandes wie auch der Schriftenreihe insgesamt ist es deshalb, entsprechende Forschungslücken durch das Beschreiten innovativer, auch Diskussion provozierender Wege zu überwinden. In present and past migration processes the fate of the individual becomes tangible much faster than in many other historical processes. Hence, it is not uncommon that people take sides with the migrant and possibly also of his or her country of origin, even though the academia should refrain from biased judgements. Not least as a result of the "refugee crisis" of 2015, a noticeable need for orientation knowledge based on economics and economic history has developed, which historical migration research has not been able to satisfy so far. The aim of this first volume, as well as of the series as a whole, is therefore to overcome the corresponding gaps in research by taking innovative and provocative paths in order to stimulate discussion.

"Freedom in a commons brings ruin to all." So argued ecologist Garrett Hardin in "The Tragedy of the Commons" in the 13 December 1968 issue of Science (1). Hardin questioned society's ability to manage shared resources and avoid an environmentally and socially calamitous free-for-all. In the 50 years since, the essay has influenced discussions ranging from climate change (see page 1217) to evolution, from infectious disease to the internet, and has reached far beyond academic literature—but not without criticism. Considerable work, notably by Nobelist Elinor Ostrom (2) , has challenged Hardin, particularly his emphasis on property rights and government regulatory leviathans as solutions. Instead, research has documented contexts, cases, and principles that reflect the ability of groups to collectively govern common resources. To mark this anniversary and celebrate the richness of research and practice around commons and cooperation, Science invited experts to share some contemporary views on such tragedies and how to avert them. ; IFPRI3; ISI; CRP2; CRP5; 5 Strengthening Institutions and Governance; 1 Fostering Climate-Resilient and Sustainable Food Supply ; EPTD; PIM ; PR ; CGIAR Research Program on Policies, Institutions, and Markets (PIM); CGIAR Research Program on Water, Land and Ecosystems (WLE)

Violent ethno-nationalist conflicts continue to mar the history of the twentieth century; yet no satisfactory answer to the question of why humans are susceptible to indoctrination by ideologies that lead to inter-group hostility has so far been found. In this volume an international team of leading scientists from many different fields approach this complex issue from a biological perspective, treating indoctrinability as a predisposition that has its roots in humanity's evolutionary past