162 research outputs found
Dynamic cyclic performance of phenol-formaldehyde resin derived carbons for pre-combustion CO2 capture : An experimental study
Acknowledgments This work was carried out with financial support from the Spanish MINECO (Project ENE2011-23467), co-financed by the European Regional Development Fund (ERDF).Peer reviewedPublisher PD
Computational chemical analysis of unconjugated bilirubin anions and insights into pKa values clarification
The pKa, the negative logarithm of the acid dissociation equilibrium constant, of the carboxylic acid groups of unconjugated bilirubin in water is a discussed issue because there are quite different experimental values reported. Using quantum mechanical calculations we have studied the conformational behavior of unconjugated bilirubin species (in gas phase and in solution modeled implicitly and explicitly) to provide evidence that may clarify pKa values because of its pathophysiological relevance. Our results show that rotation of carboxylate group, which is not restricted, settles it in a suitable place to establish stronger interactions that stabilizes the monoanion and the dianion to be properly solvated, demonstrating that the rationalization used to justify the high pKa values of unconjugated bilirubin is inappropriate. Furthermore, low unconjugated bilirubin (UCB) pKa values were estimated from a linear regression analysis.Fil: Vega Hissi, Esteban Gabriel. Universidad Nacional de San Luis. Facultad de Quimica, Bioquimica y Farmacia. Departamento de Quimica; Argentina. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico San Luis. Instituto Multidisciplinario de Investigaciones BiolĂłgicas de San Luis; ArgentinaFil: Estrada, Mario Rinaldo. Universidad Nacional de San Luis. Facultad de Quimica, Bioquimica y Farmacia. Departamento de Quimica; ArgentinaFil: Lavecchia, MartĂn JosĂ©. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico La Plata. Centro de QuĂmica InorgĂĄnica; ArgentinaFil: Pis Diez, Reinaldo. Consejo Nacional de Investigaciones CientĂficas y TĂ©cnicas. Centro CientĂfico TecnolĂłgico La Plata. Centro de QuĂmica InorgĂĄnica; Argentin
Evidence for strong f -d hybridization in intermetallic ferromagnet CePdIn2
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Influencia de la alteraciĂłn meteĂłrica de dos carbones coquizables con contenido medio de materia volĂĄtil en la calidad del coque producido
A ferromagnetic EuâPt surface compound grown below hexagonal boron nitride
One of the fundamental applications for monolayer-thick 2D materials is their use as protective layers of metal surfaces and in situ intercalated reactive materials in ambient conditions. Here we investigate the structural, electronic, and magnetic properties, as well as the chemical stability in air of a very reactive metal, Europium, after intercalation between a hexagonal boron nitride (hBN) layer and a Pt substrate. We demonstrate that Eu intercalation leads to a hBN-covered ferromagnetic EuPt2 surface alloy with divalent Eu2+ atoms at the interface. We expose the system to ambient conditions and find a partial conservation of the di-valent signal and hence the EuâPt interface. The use of a curved Pt substrate allows us to explore the changes in the Eu valence state and the ambient pressure protection at different substrate planes. The interfacial EuPt2 surface alloy formation remains the same, but the resistance of the protecting hBN layer to ambient conditions is reduced, likely due to a rougher surface and a more discontinuous hBN coating
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The nature of ferromagnetism in the chiral helimagnet Cr1/3NbS2
The chiral helimagnet Cr1/3NbS2 hosts exotic spin textures, whose influence on the magneto-transport properties make this material an ideal candidate for future spintronic applications. To date, the interplay between macroscopic magnetic and transport degrees of freedom is believed to result from a reduction in carrier scattering following spin order. Here, we present electronic structure measurements across the helimagnetic transition temperature TC that challenges this view. We show that the Fermi surface is comprised of strongly hybridized Nb- and Cr-derived electronic states, and that spectral weight close to the Fermi level increases anomalously as the temperature is lowered below TC. These findings are rationalized on the basis of first principle density functional theory calculations, which reveal a large nearest-neighbor exchange energy, suggesting the interaction between local spin moments and hybridized Nb- and Cr-derived itinerant states to go beyond the perturbative interaction of Ruderman-Kittel-Kasuya-Yosida, suggesting instead a mechanism rooted in a Hundâs exchange interaction
The nature of ferromagnetism in the chiral helimagnet
The chiral helimagnet, , hosts exotic spin textures, whose
influence on the magneto-transport properties, make this material an ideal
candidate for future spintronic applications. To date, the interplay between
macroscopic magnetic and transport degrees of freedom is believed to result
from a reduction in carrier scattering following spin order. Here, we present
electronic structure measurements through the helimagnetic transition
temperature, that challenges this view by showing a Fermi surface
comprised of strongly hybridized Nb- and Cr- derived electronic states, and
spectral weight in proximity to the Fermi level to anomalously increases as
temperature is lowered below . These findings are rationalized on the
basis of first principle, density functional theory calculations, which reveal
a large nearest-neighbor exchange energy, suggesting the interaction between
local spin moments and hybridized Nb- and Cr- derived itinerant states to go
beyond the perturbative interaction of Ruderman-Kittel-Kasuya-Yosida,
suggesting instead a mechanism rooted in a Hund's exchange interaction
Physical Delithiation of Epitaxial LiCoO2 Battery Cathodes as a Platform for Surface Electronic Structure Investigation
We report a novel delithiation process for epitaxial thin films of LiCoO2(001) cathodes using only physical methods,
based on ion sputtering and annealing cycles. Preferential Li sputtering followed by annealing produces a surface layer with a Li
molar fraction in the range 0.5 < x < 1, characterized by good crystalline quality. This delithiation procedure allows the unambiguous
identification of the effects of Li extraction without chemical byproducts and experimental complications caused by electrolyte
interaction with the LiCoO2 surface. An analysis by X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy
(XAS) provides a detailed description of the delithiation process and the role of O and Co atoms in charge compensation. We
observe the simultaneous formation of Co4+ ions and of holes localized near O atoms upon Li removal, while the surface shows a (2
Ă 1) reconstruction. The delithiation method described here can be applied to other crystalline battery elements and provide
information on their properties that is otherwise difficult to obtainThis work was supported by the Spanish MICINN (grant nos.
PID2021-123295NB-I00 and PID2020-117024GB-C43),
MAT2017-83722-R, âMarĂa de Maeztuâ Programme for
Units of Excellence in R&D (CEX2018-000805-M), within
the framework of UE M-ERA.NET 2018 program under
StressLIC Project (grant no. PCI2019-103594) and by the
Comunidad AutĂłnoma de Madrid (contract no. PEJD-2019-
PRE/IND-15769 and S2108-NMT4321). The authors acknowledge Elettra Sincrotrone Trieste for providing access to
its synchrotron radiation facilities. They thank Ignacio
Carabias from the Diffraction Unit CAI UCM for his
experimental support and helpful comments. The research
leading to this result has been supported by the project
CALIPSOplus under Grant Agreement 730872 from the EU
Framework Programme for Research and Innovation HORIZON 2020. M.J., P.M., I.P., and F.B. acknowledge funding
from EUROFEL (RoadMap Esfri). The work at the University
of Maryland was supported by ONR MURI (Award No.
N00014-17-1-2661). The work at Sandia National Laboratories was supported by the Laboratory-Directed Research and
Development (LDRD) Program and the DOE Basic Energy
Sciences Award number DE-SC0021070. Sandia National
Laboratories is a multimission laboratory managed and
operated by National Technology and Engineering Solutions
of Sandia, LLC, a wholly owned subsidiary of Honeywell
International, Inc., for the US Department of Energyâs National
Nuclear Security Administration under contract DE-NA 000352
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