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Steen Lysgaard, Matthias K Christensen, Heine A Hansen, Juan Maria Garcia Lastra, Poul Norby, Tejs Vegge
Zinc-air batteries offer the potential of low cost energy storage with high energy density, but at present secondary batteries suffer from poor cyclability. To develop secondary Zn-air batteries, several challenges need to be overcome: choking of the cathode, catalyzing the oxygen evolution and reduction reactions, limiting dendrite formation and the hydrogen evolution reaction (HER). Understanding and alleviating HER at the anode is a challenge, where it is necessary to involve computational as well as experimental research...
March 30, 2018: ChemSusChem
Qingming Deng, Tiantian Wu, Guibin Chen, Heine Anton Hansen, Tejs Vegge
The CO oxidation reaction on single 3d-transition metal catalytic sites in experimentally realized tetracyanoquinodimethane (TM-TCNQ) monolayers (TM = Sc-Zn) is systematically investigated by means of first-principles calculations. Considering the stabilities, adsorption characteristics and thermodynamics of all the ten candidates (Sc-Zn), Sc-TCNQ is found to display the lowest activation energies and yield the highest catalytic activity for room temperature CO oxidation. Exploring the Langmuir-Hinshelwood (LH) and Eley-Rideal (ER) mechanisms, we find that the rate-limiting step of CO oxidation catalyzed by Sc-TCNQ (CO + O2 * → OOCO*) can follow the LH mechanism with free energy barriers as low as 0...
February 14, 2018: Physical Chemistry Chemical Physics: PCCP
Marko Melander, Elvar Ö Jónsson, Jens J Mortensen, Tejs Vegge, Juan Maria García Lastra
No abstract text is available yet for this article.
February 13, 2018: Journal of Chemical Theory and Computation
Vladimir Tripkovic, Heine Anton Hansen, Tejs Vegge
Minimizing energy and materials costs for driving the oxygen evolution reaction (OER) is paramount for the commercialization of water electrolysis cells and rechargeable metal-air batteries. Structural stability, catalytic activity, and electronic conductivity of pure and doped α-MnO2 for the OER are studied using density functional theory calculations. As model surfaces, we investigate the (110) and (100) facets, on which three possible active sites are identified: a coordination unsaturated, a bridge, and a bulk site...
February 9, 2018: ChemSusChem
M Rincón, E Díaz-López, P Selnes, K Vegge, M Altmann, T Fladby, A Bjørnerud
Brain white matter hyperintensities (WMHs) are linked to increased risk of cerebrovascular and neurodegenerative diseases among the elderly. Consequently, detection and characterization of WMHs are of significant clinical importance. We propose a novel approach for WMH segmentation from multi-contrast MRI where both voxel-based and lesion-based information are used to improve overall performance in both volume-oriented and object-oriented metrics. Our segmentation method (AMOS-2D) consists of four stages following a "generate-and-test" approach: pre-processing, Gaussian white matter (WM) modelling, hierarchical multi-threshold WMH segmentation and object-based WMH filtering using support vector machines...
July 2017: Neuroinformatics
Ask Hjorth Larsen, Jens Jørgen Mortensen, Jakob Blomqvist, Ivano E Castelli, Rune Christensen, Marcin Dułak, Jesper Friis, Michael N Groves, Bjørk Hammer, Cory Hargus, Eric D Hermes, Paul C Jennings, Peter Bjerre Jensen, James Kermode, John R Kitchin, Esben Leonhard Kolsbjerg, Joseph Kubal, Kristen Kaasbjerg, Steen Lysgaard, Jón Bergmann Maronsson, Tristan Maxson, Thomas Olsen, Lars Pastewka, Andrew Peterson, Carsten Rostgaard, Jakob Schiøtz, Ole Schütt, Mikkel Strange, Kristian S Thygesen, Tejs Vegge, Lasse Vilhelmsen, Michael Walter, Zhenhua Zeng, Karsten W Jacobsen
The atomic simulation environment (ASE) is a software package written in the Python programming language with the aim of setting up, steering, and analyzing atomistic simulations. In ASE, tasks are fully scripted in Python. The powerful syntax of Python combined with the NumPy array library make it possible to perform very complex simulation tasks. For example, a sequence of calculations may be performed with the use of a simple 'for-loop' construction. Calculations of energy, forces, stresses and other quantities are performed through interfaces to many external electronic structure codes or force fields using a uniform interface...
July 12, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Simon Loftager, Juan María García-Lastra, Tejs Vegge
Lithium iron borate (LiFeBO3 ) is a promising cathode material due to its high theoretical specific capacity, inexpensive components and small volume change during operation. Yet, challenges related to severe air- and moisture-induced degradation have prompted the utilization of a protective coating on the electrode which also improves the electronic conductivity. However, not much is known about the preferential geometries of the coating as well as how these coating-electrode interfaces influence the lithium diffusion between the coating and the electrode...
January 18, 2017: Physical Chemistry Chemical Physics: PCCP
A D Vitger, B M Stallknecht, J E Miles, S L Hansen, A Vegge, C R Bjørnvad
The influence of physical activity on metabolic health in overweight dogs is unknown. This study was conducted to evaluate biomarkers of immunometabolic health in relation to changes in physical activity and adiposity. Client-owned overweight dogs participated in a 12-wk intervention based on caloric restriction combined with a training program (fitness and diet [FD] group, n = 8), or caloric restriction alone (diet-only [DO] group, n = 8). Physical activity was monitored by accelerometry. All dogs were fed the same diet and achieved similar weight loss...
April 2017: Domestic Animal Endocrinology
Christina S Vegge, Melissa J Jansen van Rensburg, Janus J Rasmussen, Martin C J Maiden, Lea G Johnsen, Morten Danielsen, Sheila MacIntyre, Hanne Ingmer, David J Kelly
Isolates of the zoonotic pathogen Campylobacter are generally considered to be unable to metabolize glucose due to lack of key glycolytic enzymes. However, the Entner-Doudoroff (ED) pathway has been identified in Campylobacter jejuni subsp. doylei and a few C. coli isolates. A systematic search for ED pathway genes in a wide range of Campylobacter isolates and in the C. jejuni/coli PubMLST database revealed that 1.7% of >6,000 genomes encoded a complete ED pathway, including both C. jejuni and C. coli from diverse clinical, environmental and animal sources...
2016: Frontiers in Microbiology
Lisa Flem Kalheim, Per Selnes, Atle Bjørnerud, Christopher Coello, Kjetil Vegge, Tormod Fladby
Alzheimer's disease (AD) is the most prevalent neurodegenerative disorder and cause of dementia and is characterized by amyloid plaques and neurofibrillary tangles. AD has traditionally been considered to primarily affect gray matter, but multiple lines of evidence also indicate white matter (WM) pathology and associated small-vessel cerebrovascular disease. WM glucose delivery and metabolism may have implications for local tissue integrity, and [(18)F]-fluorodeoxyglucose positron emission tomography (FDG-PET) may be helpful to assess neuroglial and axonal function in WM...
2016: Frontiers in Neurology
Arghya Bhowmik, Tejs Vegge, Heine A Hansen
A detailed understanding of the electrochemical reduction of CO2 into liquid fuels on rutile metal oxide surfaces is developed by using DFT calculations. We consider oxide overlayer structures on RuO2 (1 1 0) surfaces as model catalysts to elucidate the trends and limitations in the CO2 reduction reaction (CO2RR) based on thermodynamic analysis. We aim to specify the requirements for CO2RR catalysts to establish adsorbate scaling relations and use these to derive activity volcanoes. Computational results show that the OH* binding free energy is a good descriptor of the thermodynamic limitations and it defines the left leg of the activity volcano for CO2RR...
November 23, 2016: ChemSusChem
Marko Melander, Elvar Ö Jónsson, Jens J Mortensen, Tejs Vegge, Juan Maria García Lastra
Combining constrained density function theory (cDFT) with Marcus theory is an efficient and promising way to address charge transfer reactions. Here, we present a general and robust implementation of cDFT within the projector augmented wave (PAW) framework. PAW pseudopotentials offer a reliable frozen-core electron description across the whole periodic table, with good transferability, as well as facilitate the extraction of all-electron quantities. The present implementation is applicable to two different wave function representations, atomic-centered basis sets (LCAO) and the finite-difference (FD) approximation utilizing real-space grids...
November 8, 2016: Journal of Chemical Theory and Computation
Paul C Jennings, Steen Lysgaard, Heine A Hansen, Tejs Vegge
Ternary Pt-Au-M (M = 3d transition metal) nanoparticles show reduced OH adsorption energies and improved activity for the oxygen reduction reaction (ORR) compared to pure Pt nanoparticles, as obtained by density functional theory. The strain and ligand effects in nanoparticles are decoupled and correlated with the extended Pt(111) surface for benchmarking. The ternary metal in the core allows for tuning the catalytic activity through strain effects. Pt-Au-M for M = Cr, Mn, Co, Cu, Zn nanoparticles are of particular interest as they exhibit an optimal contribution of strain, ligand effects and stability...
September 21, 2016: Physical Chemistry Chemical Physics: PCCP
Pingping Jiang, Andreas Vegge, Thomas Thymann, Jennifer Man-Fan Wan, Per Torp Sangild
BACKGROUND: Exogenous glucagon-like peptide 2 (GLP-2) stimulates intestinal adaptation after resection in animal models of pediatric short bowel syndrome (SBS). It is unknown whether the molecular mechanisms of such GLP-2 effects are similar to those of postresection spontaneous adaptation. Using preterm pigs as a model, we hypothesized that GLP-2 treatment would change the intestinal proteome within the first week after resection, relative to individuals not resected or resected without GLP-2 treatment...
August 1, 2016: JPEN. Journal of Parenteral and Enteral Nutrition
Bent R Rønnestad, Joar Hansen, Geir Vegge, Iñigo Mujika
Endurance athletes usually achieve performance peaks with 2-4 weeks of overload training followed by 1-3weeks of tapering. With a tight competition schedule, this may not be appropriate. This case investigates the effect of a 7-day overload period including daily high-intensity aerobic training followed by a 5-day step taper between two competitions in an elite cross-country mountain biker. Pre-test peak oxygen consumption was 89 ml·kg(-1)·min(-1), peak aerobic power 6.8 W·kg(-1), power output at 2 mmol·L(-1) blood lactate concentration 3...
July 2017: Journal of Sports Sciences
Helle G Olsen, Mads Kjelgaard-Hansen, Pernille Tveden-Nyborg, Malene M Birck, Karsten P Hammelev, Andreas Vegge, Bent Aalbæk, Páll S Leifsson, Henrik E Jensen, Tine Iburg, Peter M H Heegaard, Ole L Nielsen
BACKGROUND: A porcine model of haematogenous Staphylococcus aureus sepsis has previously been established in our research group. In these studies, pigs developed severe sepsis including liver dysfunction during a 48 h study period. As pigs were awake during the study, animal welfare was challenged by the severity of induced disease, which in some cases necessitated humane euthanasia. A pilot study was therefore performed in order to establish the sufficient inoculum concentration and application protocol needed to produce signs of liver dysfunction within limits of our pre-defined humane endpoints...
February 16, 2016: BMC Research Notes
Lisa F Kalheim, Atle Bjørnerud, Tormod Fladby, Kjetil Vegge, Per Selnes
Accumulating evidence suggests associations between cerebrovascular disease (CVD) and Alzheimer's disease (AD). White matter hyperintensities of presumed vascular origin (WMHs) are increased in subjects with mild cognitive impairment (MCI) and AD, but the exact pathomechanistic link is unknown. The current study investigated effects of amyloid dysmetabolism on the microstructure of WMHs in subjects with MCI or subjective cognitive decline (N = 51), dichotomized according to pathological or normal levels of amyloid-β peptide (Aβ42 ) in cerebrospinal fluid (CSF)...
January 2017: Journal of Cerebral Blood Flow and Metabolism
Jong Suk Yoo, Rune Christensen, Tejs Vegge, Jens K Nørskov, Felix Studt
The electrochemical reduction (electroreduction) of CO2 to formic acid (HCOOH) and its competing reactions, that is, the electroreduction of CO2 to CO and the hydrogen evolution reaction (HER), on twenty-seven different metal surfaces have been investigated using density functional theory (DFT) calculations. Owing to a strong linear correlation between the free energies of COOH* and H*, it seems highly unlikely that the electroreduction of CO2 to HCOOH via the COOH* intermediate occurs without a large fraction of the current going to HER...
February 19, 2016: ChemSusChem
Qiang Fu, Luis César Colmenares Rausseo, Umberto Martinez, Paul Inge Dahl, Juan Maria García Lastra, Per Erik Vullum, Ingeborg-Helene Svenum, Tejs Vegge
Antimony-doped tin dioxide (ATO) is considered a promising support material for Pt-based fuel cell cathodes, displaying enhanced stability over carbon-based supports. In this work, the effect of Sb segregation on the conductance and catalytic activity at Pt/ATO interface was investigated through a combined computational and experimental study. It was found that Sb-dopant atoms prefer to segregate toward the ATO/Pt interface. The deposited Pt catalysts, interestingly, not only promote Sb segregation, but also suppress the occurrence of Sb(3+) species, a charge carrier neutralizer at the interface...
December 23, 2015: ACS Applied Materials & Interfaces
Reza Younesi, Ane Christiansen, Simon Loftager, Juan Maria García-Lastra, Tejs Vegge, Poul Norby, Peter Holtappels
Possible changes in the oxidation state of the oxygen ion in the lithium iron phosphate Li3Fe2(PO4)3 at high voltages in lithium-ion (Li-ion) batteries are studied using experimental and computational analysis. Results obtained from synchrotron-based hard X-ray photoelectron spectroscopy and density functional theory (DFT) show that the oxidation state of O(2-) ions is altered to higher oxidation states (O(δ-), δ<2) upon charging Li3Fe2(PO4)3 to 4.7 V.
October 12, 2015: ChemSusChem
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