| 991. |
- John Mukkattukavil, Deepak, et al.
(författare)
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Resonant inelastic soft x-ray scattering on LaPt2Si2
- 2022
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Ingår i: Journal of Physics. - : IOP Publishing. - 0953-8984 .- 1361-648X. ; 34:32, s. 324003-
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Tidskriftsartikel (refereegranskat)abstract
- X-ray absorption and resonant inelastic x-ray scattering spectra of LaPt2Si2 single crystal at the Si 2p and La 4d edges are presented. The data are interpreted in terms of density functional theory, showing that the Si spectra can be described in terms of Si s and d local partial density of states (LPDOS), and the La spectra are due to quasi-atomic local 4f excitations. Calculations show that Pt d-LPDOS dominates the occupied states, and a sharp localized La f state is found in the unoccupied states, in line with the observations.
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| 992. |
- Johnson, Magnus, et al.
(författare)
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Mechanisms of the CO2 Insertion into (PCP) Palladium Allyl and Methyl sigma-Bonds. A Kinetic and Computational Study
- 2010
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Ingår i: Organometallics. - : American Chemical Society (ACS). - 0276-7333 .- 1520-6041. ; 29:16, s. 3521-3529
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Tidskriftsartikel (refereegranskat)abstract
- The reaction of the sigma-bonded (PCP)Pd-Me complex (PCP = 2,6-bis[(di-tert-butylphosphino)methyl]phenyl) with CO2 is first-order in palladium and first-order in CO, with a rate constant k(s) = 8.9 +/- 0.8 M-1 s(-1) at 353 K. Activation parameters are Delta H double dagger = 73 7 kJ/mol and Delta S double dagger = 118 +/- 19 J/K mol. Based on this and theoretical calculations we propose an S(E)2 mechanism where the coordinated methyl group attacks a completely noncoordinated carbon dioxide molecule in a bimolecular reaction. The PCPPd-crotyl complex was synthesized in an 65:35 E:Z mixture, and it was shown to react with CO, to give the complex PCPPd-O(CO)CH(CH3)CHCH2 as a single isomer, where the former gamma-carbon has been carboxylated. Theoretical calculations again suggest an S(E)2 mechanism with a noncoordinated carbon dioxide reacting with the terminal carbon on the allyl group, forming an eta(2)-bonded olefin complex as an intermediate. The rearrangement of this intermediate to the O-bonded product is concluded to be rate determining. The crystal structure of PCPPd-O(CO)C(CH3)(2)CHCH2 is reported and as well as the solubility of carbon dioxide in benzene-d(6) at different pressures and temperatures.
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| 993. |
- Johnson, Magnus, et al.
(författare)
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Preparation of potentially porous, chiral organometallic materials through spontaneous resolution of pincer palladium conformers
- 2013
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42:23, s. 8484-8491
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Tidskriftsartikel (refereegranskat)abstract
- Understanding the mechanism by which advanced materials assemble is essential for the design of new materials with desired properties. Here, we report a method to form chiral, potentially porous materials through spontaneous resolution of conformers of a PCP pincer palladium complex ({2,6-bis[(di-t-butyl-phosphino)methyl]phenyl}palladium(II)halide). The crystallisation is controlled by weak hydrogen bonding giving rise to chiral qtz-nets and channel structures, as shown by 16 such crystal structures for X = Cl and Br with various solvents like pentane and bromobutane. The fourth ligand (in addition to the pincer ligand) on palladium plays a crucial role; the chloride and the bromide primarily form hexagonal crystals with large 1D channels, whereas the iodide (presumably due to its inferior hydrogen bonding capacity) forms monoclinic crystals without channels. The hexagonal channels are completely hydrophobic and filled with disordered solvent molecules. Upon heating, loss of the solvent occurs and the hexagonal crystals transform into other non-porous polymorphs. Also by introducing a strong acid, the crystallisation process can be directed to a different course, giving several different non-porous polymorphs. In conclusion, a number of rules can be formulated dictating the formation of hexagonal channel structures based on pincer palladium complexes. Such rules are important for a rational design of future self-assembling materials with applications in storage and molecular recognition.
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| 994. |
- Johnson, Magnus, et al.
(författare)
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Reactivity of NHC Au(I)-C sigma-bonds with electrophiles. An investigation of their possible involvement in catalytic C-C bond formation
- 2011
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Ingår i: CHEM SCI. - : Royal Society of Chemistry (RSC). - 2041-6520 .- 2041-6539. ; 2:12, s. 2373-2377
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Tidskriftsartikel (refereegranskat)abstract
- The first example of the reaction of an isolated gold(I) complex with an aryl halide to form a C-C bond is reported. The reactivity of (NHC) Au(I)-R complexes towards a wide range of electrophiles was investigated. The Au-C sigma-bond is shown to exhibit low nucleophilicity, but it is reactive towards MeI and MeOTf to form toluene, biphenyl and ethane, most likely through an oxidative mechanism. Carbon dioxide is completely unreactive. The experimental findings are supported by theoretical calculations.
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| 995. |
- Jonasson, Klara, et al.
(författare)
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Reversible -Hydrogen and -Alkyl Elimination in PC(sp(3))P Pincer Complexes of Iridium
- 2015
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Ingår i: Angewandte Chemie International Edition. - : Wiley. - 1433-7851 .- 1521-3773. ; 54:32, s. 9372-9375
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Tidskriftsartikel (refereegranskat)abstract
- Despite significant progress in recent years, the cleavage of unstrained C(sp(3))C(sp(3)) bonds remains challenging. A CC coupling and cleavage reaction in a PC(sp(3))P iridium pincer complex is mechanistically studied; the reaction proceeds via the formation of a carbene intermediate and can be described as a competition between -hydrogen and -alkyl elimination; the latter process was observed experimentally and is an unusual way of C(sp(3))C(sp(3)) bond scission, which has previously not been studied in detail. Mechanistic details that are based upon kinetic studies, activation parameters, and DFT calculations are also discussed. A full characterization of a CC agostic intermediate is presented.
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| 996. |
- Jonsson, B. Lars G., et al.
(författare)
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Stored energies in electric and magnetic current densities for small antennas
- 2015
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Ingår i: Proceedings of the Royal Society. Mathematical, Physical and Engineering Sciences. - : The Royal Society. - 1364-5021 .- 1471-2946. ; 471:2176
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Tidskriftsartikel (refereegranskat)abstract
- Electric andmagnetic currents are essential to describe electromagnetic-stored energy, and the associated antenna Q and the partial directivity to antenna Q-ratio, D/Q, for arbitrarily shaped structures. The upper bound of previous D/Q results for antennas modelled by electric currents is accurate enough to be predictive. This motivates us to develop the analysis required to determine upper and/or lower bounds for electromagnetic problems that include magnetic model currents. Here we derive new expressions for the stored energies, which are used to determine antenna Q bounds and D/Q bounds for the combination of electric and magnetic currents, in the limit of electrically small antennas. In this investigation, we show both new analytical results and we illustrate numerical realizations of them. We show that the lower bound of antenna Q is inversely proportional to the largest eigenvalue of certain combinations of the electric and magnetic polarizability tensors. These results are an extension of the electric only currents, which come as a special case. The proposed method to determine the minimum Q-value which is based on the new expressions for the stored energies, also yields a family of current-density minimizers for optimal electric and magnetic currents that can lend insight into antenna designs.
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| 997. |
- Jonsson, Daniel K., et al.
(författare)
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Energy security and climate change mitigation as combined areas of analysis in contemporary research
- 2013
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Ingår i: Energy studies review. - 0843-4379. ; 20:2, s. 90-112
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Tidskriftsartikel (refereegranskat)abstract
- Climate change mitigation and energy security are partly interacting areas that both present future challenges. The extensive research underway within these areas is mainly conducted in separate research communities, although there are some integrative efforts. This paper examines the breadth and heterogeneity involved in treating energy security and climate change mitigation as a combined research area. The outcome is a comprehensive analytical framework which considers energy security aspects, climate change mitigation strategies, temporal scope and future perspective, analytical focus, approaches and methodologies, geographical scope, and scientific traditions and perspectives.
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| 998. |
- Jonsson, Daniel K., et al.
(författare)
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Energy security matters in the EU Energy Roadmap
- 2015
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Ingår i: Energy Strategy Reviews. - : Elsevier. - 2211-467X .- 2211-4688. ; 6, s. 48-56
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Tidskriftsartikel (refereegranskat)abstract
- Energy security has gained increasing prominence on the EU political agenda, but is often framed narrowly, in terms of import dependency or security of supply. In this paper we screen and scope out a more comprehensive suite of energy security aspects to be considered when assessing low-carbon energy scenarios and apply it using the EU Energy Roadmap as an example. Availability and affordability issues as well as security of demand matters and geopolitical security aspects are identified and discussed. External factors, e.g., future international climate treaties and international relations, are important for some energy security outcomes. A broader framing of energy security together with structured assessments on the security implications of energy transitions would benefit future EU energy policy.
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| 999. |
- Jonsson, Leif, et al.
(författare)
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Automated Bug Assignment: Ensemble-based Machine Learning in Large Scale Industrial Contexts
- 2015
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Ingår i: Empirical Software Engineering. - : Springer Science and Business Media LLC. - 1573-7616 .- 1382-3256. ; 21:4
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Tidskriftsartikel (refereegranskat)abstract
- Bug report assignment is an important part of software maintenance. In particular, incorrect assignments of bug reports to development teams can be very expensive in large software development projects. Several studies propose automating bug assignment techniques using machine learning in open source software contexts, but no study exists for large-scale proprietary projects in industry. The goal of this study is to evaluate automated bug assignment techniques that are based on machine learning classification. In particular, we study the state-of-the-art ensemble learner Stacked Generalization (SG) that combines several classifiers. We collect more than 50,000 bug reports from five development projects from two companies in different domains. We implement automated bug assignment and evaluate the performance in a set of controlled experiments. We show that SG scales to large scale industrial application and that it outperforms the use of individual classifiers for bug assignment, reaching prediction accuracies from 50 % to 89 % when large training sets are used. In addition, we show how old training data can decrease the prediction accuracy of bug assignment. We advice industry to use SG for bug assignment in proprietary contexts, using at least 2,000 bug reports for training. Finally, we highlight the importance of not solely relying on results from cross-validation when evaluating automated bug assignment.
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| 1000. |
- Jonsson, L., et al.
(författare)
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High expression of RNA-binding motif protein 3 in esophageal and gastric adenocarcinoma correlates with intestinal metaplasia-associated tumours and independently predicts a reduced risk of recurrence and death
- 2014
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Ingår i: Biomarker Research. - : BioMed Central Ltd.. - 2050-7771. ; 2:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: High nuclear expression of the RNA-binding motif protein 3 (RBM3) has previously been found to correlate with favourable clinicopathological characteristics and a prolonged survival in several cancer forms. Here, we examined the clinicopathological correlates and prognostic significance of RBM3 expression in tumours from a consecutive cohort of upper gastrointestinal adenocarcinoma.Material and methods: Immunohistochemical RBM3 expression was analysed in tissue microarrays with primary radiotherapy- and chemotherapy-naive adenocarcinoma of the esophagus, gastroesophageal junction and stomach (n = 173). In addition paired samples of normal squamous epithelium (n = 53), gastric mucosa (n = 117), Barrett's esophagus/gastric intestinal metaplasia (n = 61) and lymph node metastases (n = 71) were analysed. Kaplan-Meier analysis and Cox proportional hazards modelling was applied to assess the impact of RBM3 expression on overall survival (OS) and recurrence-free survival (RFS).Results: RBM3 expression was similar in primary tumours and lymph node metastases, but significantly higher in primary tumours and metastases arising in a background of intestinal metaplasia compared with cases without intestinal metaplasia (p < 0.001). RBM3 expression was significantly reduced in more advanced tumour stages (p = 0.006). Low RBM3 expression was significantly associated with a shorter OS in cases with radically resected (R0) tumours (HR 2.19, 95% CI 1.33-3.61, p = 0.002) and RFS in curatively treated patients with R0 resection/distant metastasis-free disease (HR = 3.21, 95% CI 1.64-6.30, p = 0.001). These associations remained significant in adjusted analysis (HR = 1.95, 95% CI 1.17-3.25, p = 0.010 for OS and HR = 3.02, 95% CI 1.45-6.29, p = 0.003 for RFS).Conclusion: High expression of RBM3 may signify a subset of upper gastrointestinal cancers arising in a background of intestinal metaplasia and independently predicts a reduced risk of recurrence and death in patients with these cancer forms. These findings are of potential clinical utility and merit further validation.
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