| 1. |
- Karlström, Olov, et al.
(författare)
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Increasing thermoelectric performance using coherent transport
- 2011
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Ingår i: Physical Review B (Condensed Matter and Materials Physics). - 1098-0121. ; 84:11
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Tidskriftsartikel (refereegranskat)abstract
- We show that coherent electron transport through zero-dimensional systems can be used to tailor the shape of the system's transmission function. This quantum-engineering approach can be used to enhance the performance of quantum dots or molecules in thermal-to-electric power conversion. Specifically, we show that electron interference in a two-level system can substantially improve the maximum thermoelectric power and the efficiency at maximum power by suppressing parasitic charge flow near the Fermi energy and by reducing electronic heat conduction. We discuss possible realizations of this approach in molecular junctions or quantum dots.
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| 2. |
- Weber, Tobias A, et al.
(författare)
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γ-Secretase modulators show selectivity for γ-secretase-mediated amyloid precursor protein intramembrane processing.
- 2022
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Ingår i: Journal of cellular and molecular medicine. - : Wiley. - 1582-4934 .- 1582-1838. ; 26:3, s. 880-892
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Tidskriftsartikel (refereegranskat)abstract
- The aggregation of β-amyloid peptide 42 results in the formation of toxic oligomers and plaques, which plays a pivotal role in Alzheimer's disease pathogenesis. Aβ42 is one of several Aβ peptides, all of Aβ30 to Aβ43 that are produced as a result of γ-secretase-mediated regulated intramembrane proteolysis of the amyloid precursor protein. γ-Secretase modulators (GSMs) represent a promising class of Aβ42-lowering anti-amyloidogenic compounds for the treatment of AD. Gamma-secretase modulators change the relative proportion of secreted Aβ peptides, while sparing the γ-secretase-mediated processing event resulting in the release of the cytoplasmic APP intracellular domain. In this study, we have characterized how GSMs affect the γ-secretase cleavage of three γ-secretase substrates, E-cadherin, ephrin type A receptor 4 (EphA4) and ephrin type B receptor 2 (EphB2), which all are implicated in important contexts of cell signalling. By using a reporter gene assay, we demonstrate that the γ-secretase-dependent generation of EphA4 and EphB2 intracellular domains is unaffected by GSMs. We also show that γ-secretase processing of EphA4 and EphB2 results in the release of several Aβ-like peptides, but that only the production of Aβ-like proteins from EphA4 is modulated by GSMs, but with an order of magnitude lower potency as compared to Aβ modulation. Collectively, these results suggest that GSMs are selective for γ-secretase-mediated Aβ production.
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| 3. |
- Bernhardsson, Anders, et al.
(författare)
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Direct self-consistent reaction field with Pauli repulsion : Solvation effects on methylene peroxide
- 1996
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Ingår i: Chemical Physics Letters. - : Elsevier BV. - 0009-2614 .- 1873-4448. ; 251:3-4, s. 141-149
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Tidskriftsartikel (refereegranskat)abstract
- The properties of methylene peroxide in the gas phase and water have been examined. The solution effects have been modeled with a cavity. To make it possible to optimize the geometry of the cavity, we have added an approximate description of the Pauli repulsion between the solvent and the solute. An efficient direct implementation of the calculation of multicenter multipole operators is also described. We have applied the method to calculate the electric properties of methylene peroxide, a system that is characterized by its near degeneracy between a biradical and a zwitterionic state. As expected, it is shown that solvent effects will stabilize the ionic configuration, resulting in a considerably weakened OO bond and an increased double bond character in the CO bond. The theoretical study has been performed using the multiconfigurational (CAS) SCF method and second-order perturbation theory (CASPT2).
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| 4. |
- Ceponkus, Justinas, et al.
(författare)
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Intermolecular vibrations of the water trimer, a matrix isolation study
- 2005
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Ingår i: The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory. - : American Chemical Society (ACS). - 1520-5215. ; 109:35, s. 7859-7864
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Tidskriftsartikel (refereegranskat)abstract
- Infrared spectra from 25 to 4000 cm(-1) have been recorded of water (H2O, D2O and (H2O)-O-18) matrix isolated in neon, argon, and krypton matrices. Intermolecular absorption bands of different isotopologues of the water trimer and tetramer have been assigned from concentration dependencies and diffusion behavior, using the well-known mid-infrared trimer and tetramer absorption bands as measures of the trimer and tetramer concentrations. The results are compared to ab initio calculations.
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| 5. |
- Engdahl, Anders, et al.
(författare)
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The water-hydroxyl radical complex: A matrix isolation study.
- 2003
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 118:17, s. 7797-7802
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Tidskriftsartikel (refereegranskat)abstract
- The water–hydroxyl radical complex was prepared by irradiating peroxy radicals in hydrogen-doped argon matrices. The low water content of the matrices made it possible to observe the fundamental bands of the complexed water molecule. The experimental results are compared with the results from ab initio calculations. The complex rotates around the O–O axis in the matrix. ©2003 American Institute of Physics.
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| 6. |
- Engkvist, Ola, et al.
(författare)
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On the relation between retention indexes and the interaction between the solute and the column in gas-liquid chromatography
- 1996
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Ingår i: Journal of chemical information and computer sciences. - : American Chemical Society (ACS). - 0095-2338 .- 1520-5142. ; 36:6, s. 1153-1161
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Tidskriftsartikel (refereegranskat)abstract
- Gas-liquid chromatography retention indexes for organic molecules are determined by the interaction between the molecule and the column liquid phase. In this article, a model for calculating the interaction energy between a molecule and a dielectric wall is developed. The model is at least to our knowledge the first attempt to predict retention indexes from the interaction between the molecules and the column. This approach to predict retention indexes is radically different from methods proposed before. Earlier predictions of the retention indexes have been done by a large number of descriptors, which were Linearly correlated to the retention indexes. The developed model has been tested for polycyclic aromatic hydrocarbons mainly with a molecular weight of 302. For the molecules with MW 302 the obtained correlation coefficient is 0.92. A somewhat simpler model is used to fit PAH with different MWs. A correlation coefficient of 0.998 is obtained if the retention indexes were fitted to the logarithm of the interaction energies between the PAHs and the column.
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| 7. |
- Gagliardi, Laura, et al.
(författare)
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Local properties of quantum chemical systems : The LoProp approach
- 2004
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 121:10, s. 4494-4500
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Tidskriftsartikel (refereegranskat)abstract
- A new method is presented, which makes it possible to partition molecular properties like multipole moments and polarizabilities, into atomic and interatomic contributions. The method requires a subdivision of the atomic basis set into occupied and virtual basis functions for each atom in the molecular system. The localization procedure is organized into a series of orthogonalizations of the original basis set, which will have as a final result a localized orthonormal basis set. The new localization procedure is demonstrated to be stable with various basis sets, and to provide physically meaningful localized properties. Transferability of the methyl properties for the alkane series and of the carbon and hydrogen properties for the benzene, naphtalene, and anthracene series is demonstrated.
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| 8. |
- Gospic, Katarina, et al.
(författare)
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Altruism costs-the cheap signal from amygdala
- 2014
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Ingår i: Social Cognitive & Affective Neuroscience. - : Oxford University Press (OUP). - 1749-5016 .- 1749-5024. ; 9:9, s. 1325-1332
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Tidskriftsartikel (refereegranskat)abstract
- When people state their willingness to pay for something, the amount usually differs from the behavior in a real purchase situation. The discrepancy between a hypothetical answer and the real act is called hypothetical bias. We investigated neural processes of hypothetical bias regarding monetary donations to public goods using fMRI with the hypothesis that amygdala codes for real costs. Real decisions activated amygdala more than hypothetical decisions. This was observed for both accepted and rejected proposals. The more the subjects accepted real donation proposals the greater was the activity in rostral anterior cingulate cortex-a region known to control amygdala but also neural processing of the cost-benefit difference. The presentation of a charitable donation goal evoked an insula activity that predicted the later decision to donate. In conclusion, we have identified the neural mechanisms underlying real donation behavior, compatible with theories on hypothetical bias. Our findings imply that the emotional system has an important role in real decision making as it signals what kind of immediate cost and reward an outcome is associated with.
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| 9. |
- Hagberg, Daniel, et al.
(författare)
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On the solvation of ions in small water droplets
- 2005
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Ingår i: The Journal of Physical Chemistry Part B. - : American Chemical Society (ACS). - 1520-5207 .- 1520-6106. ; 109:9, s. 4111-4117
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Tidskriftsartikel (refereegranskat)abstract
- The solvations of positively and negatively charged model ions in water droplets have been studied using Monte Carlo simulations performed with a polarizable intermolecular potential function model. Special focus has been placed on the position of the ion in the water droplet. It was found that the sign of the ionic charge is of minor importance but an increased ionic charge localizes the ion to the central regions of the droplet, whereas a large polarizability and a large ionic radius favor locations close to the surface of the water droplet.
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| 10. |
- Hagberg, Daniel, et al.
(författare)
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The coordination of uranyl in water: A combined quantum chemical and molecular simulation study
- 2005
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Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 1520-5126 .- 0002-7863. ; 127:41, s. 14250-14256
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Tidskriftsartikel (refereegranskat)abstract
- The coordination environment of uranyl in water has been studied using a combined quantum mechanical and molecular dynamics approach. Multiconfigurational wave function calculations have been performed to generate pair potentials between uranyl and water. The quantum chemically determined energies have been used to fit parameters in a polarizable force field with an added charge transfer term. Molecular dynamics simulations have been performed for the uranyl ion and up to 400 water molecules. The results show a uranyl ion with five water molecules coordinated in the equatorial plane. The U-O(H2O) distance is 2.40 angstrom, which is close to the experimental estimates. A second coordination shell starts at about 4.7 angstrom from the uranium atom. No hydrogen bonding is found between the uranyl oxygens and water. Exchange of waters between the first and second solvation shell is found to occur through a path intermediate between association and interchange. This is the first fully ab initio determination of the solvation of the uranyl ion in water.
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