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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 Örn Jónsson, Jens Jørgen Mortensen, Tejs Vegge, Juan María 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 centred basis sets (LCAO) and the finite-difference (FD) approximation utilizing real-space grids...
October 17, 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 8, 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...
August 1, 2016: 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...
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 20, 2016: 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
Stian Ellefsen, Daniel Hammarström, Tor A Strand, Erika Zacharoff, Jon E Whist, Irene Rauk, Håvard Nygaard, Geir Vegge, Marita Hanestadhaugen, Mathias Wernbom, Kristoffer T Cumming, Roar Rønning, Truls Raastad, Bent R Rønnestad
Limited data exist on the efficacy of low-load blood flow-restricted strength training (BFR), as compared directly to heavy-load strength training (HST). Here, we show that 12 wk of twice-a-week unilateral BFR [30% of one repetition maximum (1RM) to exhaustion] and HST (6-10RM) of knee extensors provide similar increases in 1RM knee extension and cross-sectional area of distal parts of musculus quadriceps femoris in nine untrained women (age 22 ± 1 yr). The two protocols resulted in similar acute increases in serum levels of human growth hormone...
October 2015: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
Per Selnes, Ramune Grambaite, Mariano Rincon, Atle Bjørnerud, Leif Gjerstad, Erik Hessen, Eirik Auning, Krisztina Johansen, Ina S Almdahl, Paulina Due-Tønnessen, Kjetil Vegge, Börje Bjelke, Tormod Fladby
To investigate putative interacting or distinct pathways for hippocampal complex substructure (HCS) atrophy and cognitive affection in early-stage Alzheimer's disease (AD) and cerebrovascular disease (CVD), we recruited healthy controls, patients with mild cognitive impairment (MCI) and poststroke patients. HCSs were segmented, and quantitative white-matter hyperintensity (WMH) load and cerebrospinal fluid (CSF) amyloid-β concentrations were determined. The WMH load was higher poststroke. All examined HCSs were smaller in amyloid-positive MCI than in controls, and the subicular regions were smaller poststroke...
November 2015: Journal of Cerebral Blood Flow and Metabolism
Steen Lysgaard, Jón S G Mýrdal, Heine A Hansen, Tejs Vegge
Using a DFT-based genetic algorithm (GA) approach, we have determined the most stable structure and stoichiometry of a 309-atom icosahedral AuCu nanoalloy, for potential use as an electrocatalyst for CO2 reduction. The identified core-shell nano-particle consists of a copper core interspersed with gold atoms having only copper neighbors and a gold surface with a few copper atoms in the terraces. We also present an adsorbate-dependent correction scheme, which enables an accurate determination of adsorption energies using a computationally fast, localized LCAO-basis set...
November 14, 2015: Physical Chemistry Chemical Physics: PCCP
Vladimir Tripkovic, Heine Anton Hansen, Jan Rossmeisl, Tejs Vegge
Further advances in fuel cell technologies are hampered by kinetic limitations associated with the sluggish cathodic oxygen reduction reaction. We have investigated a range of different formulations of binary and ternary Pt, Pd and Au thin films as electrocatalysts for oxygen reduction. The most active binary thin films are near-surface alloys of Pt with subsurface Pd and certain PdAu and PtAu thin films with surface and/or subsurface Au. The most active ternary thin films are with pure metal Pt or Pd skins with some degree of Au in the surface and/or subsurface layer and the near-surface alloys of Au with mixed Pt-Pd skins...
May 7, 2015: Physical Chemistry Chemical Physics: PCCP
Håvard Nygaard, Gunnar Slettaløkken, Geir Vegge, Ivana Hollan, Jon Elling Whist, Tor Strand, Bent R Rønnestad, Stian Ellefsen
PURPOSE: Irisin is a recently identified exercise-induced hormone that increases energy expenditure, at least in rodents. The main purpose of this study was to test the hypothesis that Irisin increases acutely in blood after singular sessions of intense endurance exercise (END) and heavy strength training (STR). Secondary, we wanted to explore the relationship between body composition and exercise-induced effects on irisin, and the effect of END and STR on muscular expression of the irisin gene FNDC5...
2015: PloS One
Jonathan Højberg, Bryan D McCloskey, Johan Hjelm, Tejs Vegge, Keld Johansen, Poul Norby, Alan C Luntz
Lithium-O2 (Li-O2) batteries are currently limited by a large charge overpotential at practically relevant current densities, and the origin of this overpotential has been heavily debated in the literature. This paper presents a series of electrochemical impedance measurements suggesting that the increase in charge potential is not caused by an increase in the internal resistance. It is proposed that the potential shift is instead dictated by a mixed potential of parasitic reactions and Li2O2 oxidation. The measurements also confirm that the rapid potential loss near the end of discharge ("sudden death") is explained by an increase in the charge transport resistance...
February 25, 2015: ACS Applied Materials & Interfaces
Martine C Holst Sørensen, Yilmaz Emre Gencay, Tina Birk, Signe Berg Baldvinsson, Claudia Jäckel, Jens A Hammerl, Christina S Vegge, Horst Neve, Lone Brøndsted
In this study we isolated novel bacteriophages, infecting the zoonotic bacterium Campylobacter jejuni. These phages may be used in phage therapy of C. jejuni colonized poultry to prevent spreading of the bacteria to meat products causing disease in humans. Many C. jejuni phages have been isolated using NCTC12662 as the indicator strain, which may have biased the selection of phages. A large group of C. jejuni phages rely on the highly diverse capsular polysaccharide (CPS) for infection and recent work identified the O-methyl phosphoramidate modification (MeOPN) of CPS as a phage receptor...
2015: PloS One
M M Birck, A Vegge, S G Moesgaard, T Eriksen
Oral dosing by gavage is often used to test compounds in minipigs. This method is also used for certain nutritional studies that require exact dosing. This procedure may be stressful for the animal and requires the assistance of more than one technician. We investigated whether a gastrostomy tube could be placed and maintained in Göttingen minipigs using a single port laparoscopic technique. As part of another study, laparoscopic gastrostomy tube placement was performed in 12 Göttingen minipigs (32 ± 2 kg) under general anesthesia...
July 2015: Laboratory Animals
Per T Sangild, Denise M Ney, David L Sigalet, Andreas Vegge, Douglas Burrin
Intestinal failure (IF), due to short bowel syndrome (SBS), results from surgical resection of a major portion of the intestine, leading to reduced nutrient absorption and need for parenteral nutrition (PN). The incidence is highest in infants and relates to preterm birth, necrotizing enterocolitis, atresia, gastroschisis, volvulus, and aganglionosis. Patient outcomes have improved, but there is a need to develop new therapies for SBS and to understand intestinal adaptation after different diseases, resection types, and nutritional and pharmacological interventions...
December 15, 2014: American Journal of Physiology. Gastrointestinal and Liver Physiology
Signe Berg Baldvinsson, Martine C Holst Sørensen, Christina S Vegge, Martha R J Clokie, Lone Brøndsted
Previous studies have identified a specific modification of the capsular polysaccharide as receptor for phages that infect Campylobacter jejuni. Using acapsular kpsM mutants of C. jejuni strains NCTC11168 and NCTC12658, we found that bacteriophage F341 infects C. jejuni independently of the capsule. In contrast, phage F341 does not infect C. jejuni NCTC11168 mutants that either lack the flagellar filaments (ΔflaAB) or that have paralyzed, i.e., nonrotating, flagella (ΔmotA and ΔflgP). Complementing flgP confirmed that phage F341 requires rotating flagella for successful infection...
November 2014: Applied and Environmental Microbiology
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