| 1. |
|
|
| 2. |
- Peters, Bram B. C., et al.
(författare)
-
Stereoselective Iridium-N,P-Catalyzed Double Hydrogenation of Conjugated Enones to Saturated Alcohols
- 2022
-
Ingår i: Journal of the American Chemical Society. - : American Chemical Society (ACS). - 0002-7863 .- 1520-5126. ; 144:19, s. 8734-8740
-
Tidskriftsartikel (refereegranskat)abstract
- Asymmetric hydrogenation of prochiral substrates such as ketones and olefins constitutes an important instrument for the construction of stereogenic centers, and a multitude of catalytic systems have been developed for this purpose. However, due to the different nature of the π-system, the hydrogenation of olefins and ketones is normally catalyzed by different metal complexes. Herein, a study on the effect of additives on the Ir-N,P-catalyzed hydrogenation of enones is described. The combination of benzamide and the development of a reactive catalyst unlocked a novel reactivity mode of Crabtree-type complexes toward C═O bond hydrogenation. The role of benzamide is suggested to extend the lifetime of the dihydridic iridium intermediate, which is prone to undergo irreversible trimerization, deactivating the catalyst. This unique reactivity is then coupled with C═C bond hydrogenation for the facile installation of two contiguous stereogenic centers in high yield and stereoselectivity (up to 99% ee, 99/1 d.r.) resulting in a highly stereoselective reduction of enones.
|
|
| 3. |
- Jacob, Stefan
(författare)
-
Cochlear mechanics : design and application of superresolution techniques in the cochlear apex
- 2011
-
Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Hearing is one of the five traditional senses. Next to vision it is probably the most important for man and plays a crucial role in day-to-day communication. However, hearing is extremely challenged by modern life style, due to increasing noise exposure and aging societies. Ten percent of the world population is estimated to be hearing impaired. Unfortunately, most conditions cannot be treated sufficiently, a fact often attributed to the very limited understanding of inner ear workings. Early on, it was recognized that the sensitivity of the ear is dramatically enhanced by an active process, termed cochlear amplification, which remains enigmatic. The first part of this thesis presents two complementary optical techniques to measure vibration amplitudes, which are orders of magnitude smaller than the wavelength of light. Both methods are adapted to probe the physiologically relevant low frequency part of the organ of Corti, which is responsible for speech reception. In the second part of the thesis we employ these methods to investigate the role of the large electrochemical potential surrounding the hearing organ. This endogenous extracellular potential is hypothesized to play an important role in cochlear amplification, but its immediate impact on cochlear mechanics is highly speculative. We show that the endocochlear potential leads to sustained deformations of the hearing organ and spatially distinctive alterations of the mechanical response to sound perception. The third part of the thesis investigates the role of membrane cholesterol in somatic hair cell motility, which is one of two mechanisms hypothesized to underlie cochlear amplification. We show that reducing cholesterol dramatically affects the interaction of the hearing organ with the endocochlear potential.
|
|
| 4. |
- Sammelin, Monika
(författare)
-
The nature of gold in the Aitik Cu-Au deposit : implications for mineral processing and mine planning
- 2011
-
Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The Aitik mine is a large Cu-Au producer in Europe with an annual production of 28 million tons of ore and a planned expansion of production to 36 million tons of ore until year 2013. Large ongoing investments are done in the mine and a new processing plant is built to manage the capacity increase. The mine is situated 15 kilometers from the town Gällivare, in northern Norrbotten, Sweden. The ore is a large porphyry type deposit with low grades of disseminated copper (0,27 %) and gold (0,16 ppm). Porphyry copper ores usually have low recoveries when flotation is used as an extraction method and also the Aitik mine has shown historically low gold recoveries (< 50 %).The Aitik deposit is situated in 1.9 Ga Svecofennian volcanic and sedimentary rocks formed in a volcanic arc environment and later deformed and metamorphosed at amphibolite facies. The main ore zone consists of biotite and muscovite schist and gneisses. A thrust fault divides the main ore zone from the hanging wall that contains feldspar biotite amphibole gneiss. In the footwall the feldspar biotite amphibole gneiss also is found and an intrusion of quartz montzodiorite.In this study, horizontal and vertical zoning patterns were recognized in data based on the block model that consist of drill cores and drill ship samples since the mine started 1968. The vertical zoning shows a decrease in high (> 0,6 % Cu) copper grade areas and an increase in high (>0,3 ppm Au) areas towards the depth. An increase in the amphibole content is seen in the biotite gneiss towards depth. The gold mineralized areas are trending northeasterly and plunging northeast, and for copper north-northwest. The horizontal zoning can be seen in the middle of the ore zone where a high-grade area of disseminated sulfides in potassic altered biotite gneiss/schist exists. Further towards the hanging wall, a low grade, strongly sericite altered and pyrite-rich schist is common.Gold-rich areas are found close to the hanging wall in strongly sericite schist altered rock and in a part of a biotite schist that are strongly affected by K feldspar and epidote alteration and quartz and pyrite growth, but also in the amphibole rich parts close to the footwall. Copper dominated mineralization is mainly developed towards the hanging wall, as disseminated and massive veins of chalcopyrite. The rich dissemination in the centre of the ore body is suggested to be a part of the primary mineralization, and the locally higher concentrations in veins would originate from later remobilization. To get a better knowledge of how gold occurs at Aitik and how to increase the gold recovery during mining a detailed mineralogical investigation was done. This revealed that there is a change in gold associations towards depth. Commonly associated minerals with gold at 600 m and below are K-feldspar, biotite, plagioclase, quartz, chalcopyrite and pyrite. At higher levels in the mine gold is most commonly associated with chalcopyrite and pyrite. There is also a change in gold content in alloys towards depth where the gold decreases in electrum and amalgam but the amount of native gold grains increases. As the average gold and copper grades are relatively constant at the different levels in the mine this means that the gold associations that are not connected to sulfides (chalcopyrite) are going to tailings from the deeper part of the mine and the gold recovery as a consequence is lower today. Some other copper-gold deposits have implemented several different recovery methods to extract the gold from the ore, an example from Bajo de la Alumbrera (Chryssoulis 2001), Argentina with a similar ore type as Aitik have a combination of gravity and flotation in their recovery process. Based on the results on the mineralogy and the mineral associations it would be possible to combine additional recovery methods as gravimetric methods to the flotation that are used today. Lime used in the process might have a depressive affect on gold and should be further investigated. The Aitik deposit is interpreted to have a mixed origin, with an early porphyry copper style of mineralization overprinted by a later and minor iron-oxide Cu-Au (IIOCG) system (Wanhainen 2005). Gold bearing fluids at Aitik were compared with those at the minor epigenetic Cu-Au deposits Liikavaara East, Fridhem, Jårbojoki and Muorjevaara, that occur in the Nautanen deformation zone. According to earlier studies high salinity fluids are connected to the copper mineralization and in this study a connection between gold and CO2 is suggested based on the positive correlation between CO2 and gold that could be found in all deposits. However, the carbonic fluids varied in composition and includes pure CO2, CO2-CH4, CO2-H2O, or CO2 present as calcite in aqueous inclusions. The highest gold grades were associated with CO2 in silicates and CO2-CH4 in sulphides.
|
|
| 5. |
- Wang, Yi
(författare)
-
The Cause-Effect Latency Problem in Real-Time Systems
- 2018
-
Ingår i: Formal Methods For Industrial Critical Systems, FMICS 2018. - : SPRINGER INTERNATIONAL PUBLISHING AG. - 9783030002442 - 9783030002435 ; , s. XIII-XIII
-
Konferensbidrag (refereegranskat)
|
|
| 6. |
- Aleksandrova, Elena V, et al.
(författare)
-
Structural basis of Cfr-mediated antimicrobial resistance and mechanisms for its evasion
- 2023
-
Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- The ribosome is an essential drug target as many classes of clinically important antibiotics bind and inhibit its functional centers. The catalytic peptidyl transferase center (PTC) is targeted by the broadest array of inhibitors belonging to several chemical classes. One of the most abundant and clinically prevalent mechanisms of resistance to PTC-acting drugs is C8-methylation of the universally conserved adenine residue 2503 (A2503) of the 23S rRNA by the methyltransferase Cfr. Despite its clinical significance, a sufficient understanding of the molecular mechanisms underlying Cfr-mediated resistance is currently lacking. In this work, we developed a method to express a functionally-active Cfr-methyltransferase in the thermophilic bacterium Thermus thermophilus and report a set of high-resolution structures of the Cfr-modified 70S ribosome containing aminoacyl- and peptidyl-tRNAs. Our structures reveal that an allosteric rearrangement of nucleotide A2062 upon Cfr-methylation of A2503 is likely responsible for the inability of some PTC inhibitors to bind to the ribosome, providing additional insights into the Cfr resistance mechanism. Lastly, by determining the structures of the Cfr-methylated ribosome in complex with the antibiotics iboxamycin and tylosin, we provide the structural bases behind two distinct mechanisms of evading Cfr-mediated resistance.
|
|
| 7. |
- Bakker, Jan P., et al.
(författare)
-
Long-term effects of scrub clearance and litter removal on the re-establishment of dry alvar grassland species
- 2012
-
Ingår i: Annales Botanici Fennici. - 0003-3847 .- 1797-2442. ; 49:1-2, s. 21-30
-
Tidskriftsartikel (refereegranskat)abstract
- Many characteristic dry alvar grassland species disappear after cessation of livestock grazing as a result of encroachment by Juniperus communis. We studied the re-establishment of these species after scrub clearance with and without the removal of the layer of litter and mosses in long-term (14 years) permanent plots. Most of the species belonging to the community species pool of dry alvar grassland species before clearance were found in permanent plots between 2 and 14 years after the clearance. A large part originated from vegetative spread of already occurring species in the established vegetation in the surroundings. Only a small part of the long-term persistent soil seed bank resulted in the re-establishment of alvar species. There was no significant difference in the traits soil seed bank, seed weight and long-distance dispersal by wind, dung or fur of animals of established and non-established species. Removal of litter and mosses positively affected the re-establishment of alvar species.
|
|
| 8. |
- Jemt, Torsten, 1950, et al.
(författare)
-
A 3-year follow-up study on single implant treatment.
- 1993
-
Ingår i: Journal of dentistry. - 0300-5712. ; 21:4, s. 203-8
-
Tidskriftsartikel (refereegranskat)abstract
- The purpose of this study was to investigate restorative and postinsertion problems in patients provided with single implant supported restorations. Fifty consecutive single implant patients were reviewed over a period of 3 years following placement of artificial crowns. One (1.4%) of the 70 inserted implants was lost during the follow-up period, which gives a cumulative success rate of 98.5%. The most frequent complication was loosening of the single tooth abutment screw. This problem was associated with fistulas during the first year of clinical service. A more severe complication was that three adjacent teeth had to be endodontically treated due to accidental devitalization from surgical trauma during implant insertion. The mean marginal bone level adjacent to the implants was reduced 0.5 mm from crown insertion to the third annual review.
|
|
| 9. |
- Kellner, Martin, 1978-, et al.
(författare)
-
Environmentally relevant concentrations of citalopram partially inhibit feeding in the three-spine stickleback (Gasterosteus aculeatus)
- 2015
-
Ingår i: Aquatic Toxicology. - : Elsevier. - 0166-445X .- 1879-1514. ; 158, s. 165-170
-
Tidskriftsartikel (refereegranskat)abstract
- Selective Serotonin Re-uptake Inhibitors (SSRI) are mood-altering, psychotropic drugs commonly used in the treatment of depression and other psychological illnesses. Many of them are poorly degraded in sewage treatment plants and enter the environment unaltered. In laboratory studies, they have been demonstrated to affect a wide range of behaviours in aquatic organisms. In this study we investigated the effect of a three-week exposure to 0.15 and 1.5 μg/l of the SSRI citalopram dissolved in the ambient water on the feeding behaviour in three-spine stickleback (Gasterosteus aculeatus). Feeding, measured as the number of attacks performed on a piece of frozen bloodworms during a 10-min period, was reduced by 30–40% in fish exposed to both 0.15 and 1.5 μg/l citalopram. The effects of the environmentally relevant concentration 0.15 μg/l on feeding, an important fitness characteristic, suggests that the ecological significance of environmental SSRI exposure may be pronounced.
|
|
| 10. |
|
|
