| 220841. |
- Skillinghaug, Bobo, 1986-
(författare)
-
Palladium(II)-Catalysed Heck and Addition Reactions : Exploring Decarboxylative and Desulfitative Processes
- 2016
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Palladium complexes have the ability to catalyse cross-coupling of two organic moieties through the formation of transient metal-carbon bonds, thus bringing them closer to each other to facilitate the formation of a new bond. Palladium-catalysed coupling reactions are one of the most important carbon-carbon forming reactions available to organic chemists and many of these reactions rely on the reactivity of aryl-palladium complexes. The investigation of new aryl-palladium precursors is thus of great interest, especially as more sustainable and economic methods can be developed.This thesis describes the use of carboxylic acids and sodium arylsulfinates as such new arylating agents. Protocols for microwave-assisted palladium(II)-catalysed decarboxylative synthesis of electron-rich styrenes and 1,1-diarylethenes were developed. However, these transformations had very limited substrate scopes which prompted the investigation of sodium arylsulfinates as alternative arylating agents. These substrates were employed in the microwave-assisted palladium(II)-catalysed desulfitative addition to nitriles, and the substrate scope was demonstrated by combining a wide array of sodium arylsulfinates and nitriles to yield the corresponding aryl ketones. The application of the desulfitative reaction in a continuous flow setup was demonstrated, and aluminium oxide was identified as safe alternative to borosilicate glass as a reactor material. The mechanisms of the decarboxylative and desulfitative transformations were investigated by density functional theory (DFT) calculations. The desulfitative reaction was also investigated by direct electrospray ionization mass spectrometry (ESI-MS), providing further mechanistic insight. Finally, a protocol for the safe and convenient synthesis of a wide range of sodium arylsulfinates was developed.
|
|
| 220842. |
|
|
| 220843. |
- Skillinghaug, Bobo, et al.
(författare)
-
Palladium(II)-Catalyzed Desulfitative Synthesis of Aryl Ketones from Sodium Arylsulfinates and Nitriles : Scope, Limitations, and Mechanistic Studies
- 2014
-
Ingår i: Journal of Organic Chemistry. - : American Chemical Society (ACS). - 0022-3263 .- 1520-6904. ; 79:24, s. 12018-12032
-
Tidskriftsartikel (refereegranskat)abstract
- A fast and efficient protocol for the palladium(II)-catalyzed production of aryl ketones from sodium arylsulfinates and various organic nitriles under controlled microwave irradiation has been developed. The wide scope of the reaction has been demonstrated by combining 14 sodium arylsulfinates and 21 nitriles to give 55 examples of aryl ketones. One additional example illustrated that, through the choice of the nitrile reactant, benzofurans are also accessible. The reaction mechanism was investigated by electrospray ionization mass spectrometry and DFT calculations. The desulfitative synthesis of aryl ketones from nitriles was also compared to the corresponding transformation starting from benzoic acids. Comparison of the energy profiles indicates that the free energy requirement for decarboxylation of 2,6-dimethoxybenzoic acid and especially benzoic acid is higher than the corresponding desulfitative process for generating the key aryl palladium intermediate. The palladium(II) intermediates detected by ESI-MS and the DFT calculations provide a detailed understanding of the catalytic cycle.
|
|
| 220844. |
|
|
| 220845. |
- Skini, Ridha, et al.
(författare)
-
Large room temperature relative cooling power in La0.5Pr0.2Ca0.1Sr0.2MnO3
- 2020
-
Ingår i: Journal of Alloys and Compounds. - : Elsevier BV. - 0925-8388 .- 1873-4669. ; 827
-
Tidskriftsartikel (refereegranskat)abstract
- The La0.5Pr0.2Ca0.1Sr0.2MnO3 compound has been investigated as a potential candidate for room temperature magnetocaloric refrigeration. The Rietveld refinement of X-ray powder diffraction patterns confirms that the compound crystalizes in an orthorhombic phase with the Pnma space group. Rutherford backscattering spectrometry and time-of-flight elastic recoil detection analysis, verified the desired ratio of the elements in the compound. Using X-ray photoelectron spectroscopy two oxidation states of manganese (Mn), Mn4+ and Mn3+ were identified in the compound with relative amounts of 32% and 68%, respectively. The observed spin orbit splitting of the Mn-2p3/2 and Mn-2p1/2 levels was obtained as 11.7 eV. A ferromagnetic to paramagnetic transition was observed around 296 K, which makes the material interesting for magnetic cooling near room temperature. In addition, the absence of magnetic hysteresis provides another argument in favor of the studied compound. The isothermal entropy change (-deltaSm) and the relative cooling power (RCP) for a magnetic field change of 5 T were found to be 4 J/kg K and 372 J/kg, respectively. From the comparison of the values of (-deltaSm) and RCP with those obtained for the archetypal magnetocaloric material gadolinium, it is argued that our material can be considered as a potential candidate in cooling systems based on magnetic refrigeration.
|
|
| 220846. |
- Skini, Ridha, et al.
(författare)
-
Magnetocaloric effect and critical behavior in La0.8K0.2MnO3 nanoparticle
- 2021
-
Ingår i: RESULTS IN PHYSICS. - : Elsevier. - 2211-3797. ; 30
-
Tidskriftsartikel (refereegranskat)abstract
- We report on the magnetocaloric effect and critical phenomenon on La0.8K0.2MnO3 nanoparticle through a systematic magnetic and electrical measurement. The magnetic entropy change (Delta S-M) presents close values obtained from resistivity and magnetic measurements, however, with a discrepancy in the magnetic entropy maximum values. This discrepancy is due to the presence of an extrinsic effect associated with the nanometric grain size affecting the electrical behavior. Interestingly, our results show a good agreement with the calculation of the critical exponents and the temperature coefficient of resistance shows positive and negative values. The obtained critical exponents are close to that of the mean-field theory (with beta = 0.5, gamma = 1, and delta = 3). This indicates a long-range interaction between spins a consequence of the presence the presence of dipole- dipole interaction in this system.
|
|
| 220847. |
- Skini, Ridha, et al.
(författare)
-
Transport and magneto-transport properties in La0.8K0.2-xxMnO3-delta (x =0 and 0.1) manganites
- 2019
-
Ingår i: Journal of materials science. Materials in electronics. - : SPRINGER. - 0957-4522 .- 1573-482X. ; 30:18, s. 17363-17373
-
Tidskriftsartikel (refereegranskat)abstract
- We discuss the effect of the nanometric grain size on the behavior of the electrical and magnetoresistive response of La0.8K0.2-xxMnO3-delta (x = 0 and 0.1) nanocrystalline samples that were prepared by a sol-gel method. The results from transport and magneto-transport measurements evidence a robust dependence on the nanometric grain size. The temperature dependence of the resistivity was evaluated using different transport models. The results reveal a field-dependent minimum of the resistivity in the low-temperature region, which can be described in terms of intergranular spin-polarized tunneling. Remarkably, a considerable increase of the magnetoresistance (MR) with the decrease of nanoparticle size was found, which might open a new way for the search for potential candidates for magnetoresistive devices. Besides, the magnetic field dependence of the MR was also analyzed, and a distinct drop of MR at low fields was noticed. This behavior was primarily explained by the spin-polarized tunneling transport of conduction electrons across grain boundaries.
|
|
| 220848. |
- Skiniemi, Sannako, et al.
(författare)
-
Death from within
- 2019
-
Ingår i: Nature. - : Nature Publishing Group. - 0028-0836 .- 1476-4687. ; 570:7762, s. 449-450
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Some bacteria naturally transfer pieces of their DNA within and between species. Such a piece of DNA has been engineered to act as a molecular 'Trojan horse' that unleashes a toxin to selectively kill antibiotic-resistant Vibrio cholerae bacteria.
|
|
| 220849. |
- Skinnars Josefsson, Malin, 1966-, et al.
(författare)
-
Access to competence and policy- food provision in Swedish eldercare
- 2014
-
Konferensbidrag (refereegranskat)abstract
- Introduction: To provide food and meals in elderly care is a growing concern in the welfare state. Objective: Investigate and compare nutritional competence and its relation to different kind of food policies within elderly care in Swedish municipalities, in 2006 and 2013-14. Methodology: Web based questionnaires were distributed to all Swedish municipalities (N= 290) twice. Results: Access to clinical- and administrative dietitians differ between analyzed years and between sizes of municipalities. Nutritional competences correlated with local policies in 2006 and the national guideline (introduced in 2011) 2013-14. Conclusion: Municipal size and nutritional competence are central in strategic food provision work.
|
|
| 220850. |
- Skinnars Josefsson, Malin, 1966-, et al.
(författare)
-
Adherence to a regulation that aims to prevent and treat malnutrition : the case of Swedish elderly care
- 2019
-
Ingår i: Health Policy. - : Elsevier BV. - 0168-8510 .- 1872-6054. ; 123:7, s. 688-694
-
Tidskriftsartikel (refereegranskat)abstract
- Malnutrition constitutes a serious and challenging problem in elderly care. In 2015, a Swedish regulation that aims to prevent and treat malnutrition came into effect. This study set out to explore associations between level of adoption of the regulation reported as: no, started, yes, in a previous survey, and registrations in a national quality registry. Registry data on screening and actions extracted from the first trimester in 2014 (n=18967), 2016 (n=20318) and 2017 (n= 25669) represented 209, 197 and 199 of 290 Swedish municipalities respectively. A repeated measures ANOVA showed that there was no effect on screened nutritional status, Pearson's chi-square that there were minor differences in types of actions, and regression analysis that the number of actions increased on average by 0.3 due to a higher level of adoption of the regulation. Over the years studied, five actions were prominent regardless of level of adoption or screened nutritional status. Hence, to date, no firm conclusions regarding effects of the regulation can be drawn. Despite the regulatory nature, it appear as if the regulation and the level of adoption reported so far is routine in theory, although not yet leveraged to an implemented practice visible in the quality registry but instead decoupled from practice.
|
|
