Suchergebnisse

Near room-temperature magnetic and magnetocaloric properties of the compounds Pr0.63-xHoxSr0.37MnO3 (x=0, 0.05) were investigated. The parent compound Pr0.63Sr0.37MnO3 has a large magnetocaloric effect around its Curie temperatures of about 300 K. Partially replacing of Pr3+ ions with Ho3+ ions in Pr0.63Sr0.37MnO3 gives rise to disorder which leads to the decrease of the Curie temperature without a significant reduction of the magnetocaloric effect. The samples were prepared by solid state reaction and were found to be single phase by x-ray diffraction. The magnetic measurements reveal paramagnetic to ferromagnetic second order phase transitions. For the sample with x = 0, the magnetic entropy change |ΔSM| was in the range from 1.91 J/kg٠K (RCP = 42 J/kg) for μ0 ΔH = 1 T to 4.86 J/kg٠K (RCP = 184 J/kg) for μ0 ΔH = 4 T. For the sample with x = 0.05, the magnetic entropy change |ΔSM| was in the range from 1.61 J/kg٠K (RCP = 57.9 J/kg) for μ0 ΔH = 1 T to 4.38 J/kg٠K (RCP = 236 J/kg) for μ0 ΔH = 4 T and Tc = 216 K. These values recommend these materials to be potential candidates to be used in near room-temperature refrigeration applications.

Stabilized bismuth vanadate thin films are presented here as superior oxide ionic conductors, for application in solid state electrochemical devices operating near room temperature. Widely studied in the 90s in bulk form due to their unbeatable ionic conduction, this family of materials was finally discarded due to poor stability above 500 °C. Here, we however unveil the possibility of using Bi4V1.8Cu0.2O10.7 at reduced temperatures in thin film-based devices, where the material keeps its unmatched conduction properties and at the same time shows good stability over a wide oxygen partial pressure range. ; The research was supported by the Generalitat de Catalunya-AGAUR (2017 SGR 1421). This project has received funding from the European research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (ULTRASOFC, Grant Agreement number: 681146). ; Peer reviewed

The primary mechanism governing the emergence of near-room-temperature superconductivity (NRTS) in superhydrides is widely accepted to be the electron-phonon interaction. If so, the temperature-dependent resistance, R(T), in these materials should obey the Bloch-Grüneisen (BG) equation, where the power-law exponent, p, should be equal to the exact integer value of p= 5. However, there is a well-established theoretical result showing that the pure electron-magnon interaction should be manifested by p= 3, and p= 2 is the value for pure electron-electron interaction. Here we aimed to reveal the type of charge carrier interaction in the layered transition metal dichalcogenides PdTe2, high-entropy alloy (ScZrNb)0.65[RhPd]0.35 and highly-compressed elemental boron and superhydrides H3S, LaH x, PrH9 and BaH12 by fitting the temperature-dependent resistance of these materials to the BG equation, where the power-law exponent, p, is a free-fitting parameter. The results showed that the high-entropy alloy (ScZrNb)0.65[RhPd]0.35 exhibited pure electron-phonon mediated superconductivity with p = 4.9 0.4. Unexpectedly, we revealed that all studied superhydrides exhibit 1.8 < p < 3.2. This implies that it is unlikely that the electron-phonon interaction is the primary mechanism for the Cooper pairs formation in highly-compressed superhydrides, and alternative pairing mechanisms, for instance, the electron-magnon, the electron-polaron, the electron-electron and other pairing mechanisms should be considered as the origin for the emergence of NRTS in these compounds. © 2021 IOP Publishing Ltd. ; The author is grateful for financial support provided by the Ministry of Science and Higher Education of Russia (theme 'Pressure' No. AAAA-A18-118020190104-3) and by Act 211 Government of the Russian Federation, Contract No. 02.A03.21.0006.

[EN] Alkali activated binders are a new class of binding material with comparable or enhanced performance to Portland cement. These binding materials are obtained by a chemical reaction between an aluminosilicate material and a highly alkaline solution. In most cases, the setting hardening process of this binder is performed at high curing temperatures. In this paper, alkali activated mortars based on vitreous calcium aluminosilicate (VCAS) cured at room temperature are evaluated. Mechanical strength development and microstructural analysis (scanning electron microscopy, thermogravimetric analysis, X-ray diffraction and mercury intrusion porosimetry) of these materials are performed. Mortars yielded compressive strength ¡-89 MPa after 360 days. This is the first time that VCAS is used as aluminosilicate source material in the production of alkali activated mortars cured at room temperature. ; The authors acknowledge the Ministerio de Ciencia e Innovacio´ n of the Spanish Government (projecto. BIA2011-26947) and the Vitrominerals company for supplying VCAS samples. ; Mitsuuchi Tashima, M.; Soriano Martínez, L.; Monzó Balbuena, JM.; Borrachero Rosado, MV.; Paya Bernabeu, JJ. (2013). novel geopolymeric material cured at room temperature. Advances in Applied Ceramics. 112:179-183. https://doi.org/10.1179/1743676112Y.0000000056 ; S ; 179 ; 183 ; 112

For most of the twentieth century, public opinion was nearly analogous with polling. Enter social media, which has upended the social, technical, and communication contingencies upon which public opinion is constructed. This study documents how political professionals turn to social media to understand the public, charting important implications for the practice of campaigning as well as the study of public opinion itself. An analysis of in-depth interviews with 13 professionals from 2016 US presidential campaigns details how they use social media to understand and represent public opinion. I map these uses of social media onto a theoretical model, accounting for quantitative and qualitative measurement, for instrumental and symbolic purposes. Campaigns' use of social media data to infer and symbolize public opinion is a new development in the relationship between campaigns and supporters. These new tools and symbols of public opinion are shaped by campaigns and drive press coverage (McGregor 2019), highlighting the hybrid logic of the political media system (Chadwick 2017). The model I present brings much-needed attention to qualitative data, a novel aspect of social media in understanding public opinion. The use of social media data to understand the public, for all its problems of representativeness, may provide a retort to long-standing criticisms of surveys—specifically that surveys do not reveal hierarchical, social, or public aspects of opinion formation (Blumer 1948; Herbst 1998; Cramer 2016). This model highlights a need to explicate what can—and cannot—be understood about public opinion via social media.

In the industrialized countries university research and state-financed research are increasingly evaluated from the point of view of their contribution to technology transfer, industrial innovation, and the competitiveness of national industries. Political debates on the viability of orienting basic research toward practical applications are paralleled by discussions, among social scientists, about the risks and opportunities of political direction over science. These debates are the frame of reference for this study, which analyzes the differences between basic and applied research, their correlates and consequences, in high-temperature superconductor research in the Federal Republic of Germany. It will be shown that basic and applied research are fundamentally different in their social organization, their research goals, and their research strategies. These differences are in contrast to the call of science policy for more intense interaction and assimilation. Nevertheless, there are conditions under which basic or applied re searchers will partially follow "foreign" orientations and strategies. These conditions may, in part, be shaped by policy decisions.

This discussion paper provides the SST definitions. To find more about GHRSST, what GHRSST offers, which data set should you use? and what is SST, please visit this page: https://www.ghrsst.org/ghrsst-data-services/products/ ; The GHRSST Project Office is funded by the European Union (European Commission, EUMETSAT, Copernicus). Web: http://www.ghrsst.org Follow us on Twitter: https://twitter.com/GHRSST

We report on detachment nanolithography of an organic thin film at room temperature mediated by ultraviolet (UV) exposure. A nanopatterned, UV curable polyurethane acrylate (PUA) mold was placed on a spin-coated organic film made of 4,4'-bis[N-1-napthyl-N-phenyl-amino]biphenyl (NPB) under a low pressure (1-2 bar). A higher work of adhesion at the organic/mold interface induced detachment of the contacting layer on silicon or gold substrate, resulting in well-defined nanopatterns without a residual layer. The detachment was highly improved by a short-term UV exposure, rendering the film surface free from contaminant hydrocarbons with a lower cohesive force, as confirmed by Fourier transform infrared (FTIR) spectroscopy and measurements of contact angle of water. ; The work was supported by the Korea Science and Engineering Foundation (KOSEF)grant funded by the Korea government (MOST) (No. 2007-02605) and in part supported by the Micro Thermal System Research Center of Seoul National University.

One of the pioneering metal organic framework material, called MOF-2 and having the formula [Zn2(BDC)2], still continues awakening interest amongst the scientific community in spite of its layered character. However, the synthesis methods are either experimentally complicated or in two steps through the transformation of MOF-1. Here, we describe the preparation of a high-quality MOF-2 under more sustainable conditions, including room temperature, absence of any amine or any other pH-controller, partial substitution of the harmful organic solvent (N,N-dimethylformamide) by water, and by simply mixing linker and metal sources, the latter being zinc acetate, carefully selected as a function of their solubility in the solvent mixture. The optimum ratio of Zn(OAc)2·4H2O to terephthalic acid (H2BDC) is 1.74 and H2O to DMF is 3. MOF-2 [Zn2(BDC)2] has been characterized using powder X-ray diffraction, thermogravimetric analysis, N2 adsorption/desorption and scanning electron microscopy, all of them supporting the good quality of the material. ; NG acknowledges the financial support from the Spanish Ministry of Foreign Affairs-Spanish Agency for Cooperation and Development through the "Becas Institucionales" Program. ID acknowledges the CSIC for the research leave at Addis Ababa University. The authors acknowledge Spanish Government, MINECO (MAT2012-31127) and the Spanish Research Council CSIC (i-COOP014), for funding. The Chemistry Department, Addis Ababa University is also acknowledged for financial support. ; Peer Reviewed