| 1. |
- Falck, Emma, et al.
(författare)
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Interaction of fusidic acid with lipid membranes: Implications to the mechanism of antibiotic activity
- 2006
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Ingår i: Biophysical Journal. - : Elsevier BV. - 1542-0086 .- 0006-3495. ; 91:5, s. 1787-1799
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the effects of cholesterol and steroid-based antibiotic fusidic acid (FA) on the behavior of lipid bilayers using a variety of experimental techniques together with atomic-scale molecular dynamics simulations. Capillary electrophoretic measurements showed that FA was incorporated into fluid 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine membranes. Differential scanning calorimetry in turn showed that FA only slightly altered the thermodynamic properties of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) bilayers, whereas cholesterol abolished all endotherms when the mole fraction of cholesterol (X-chol) was > 0.20. Fluorescence spectroscopy was then used to further characterize the influence of these two steroids on DPPC large unilamellar vesicles. In the case of FA, our result strongly suggested that FA was organized into lateral microdomains with increased water penetration into the membrane. For cholesterol/DPPC mixtures, fluorescence spectroscopy results were compatible with the formation of the liquid-ordered phase. A comparison of FA and cholesterol-induced effects on DPPC bilayers through atomistic molecular dynamics simulations showed that both FA and cholesterol tend to order neighboring lipid chains. However, the ordering effect of FA was slightly weaker than that of cholesterol, and especially for deprotonated FA the difference was significant. Summarizing, our results show that FA is readily incorporated into the lipid bilayer where it is likely to be enriched into lateral microdomains. These domains could facilitate the association of elongation actor-G into lipid rafts in living bacteria, enhancing markedly the antibiotic efficacy of FA.
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| 2. |
- Helama, Samuli, et al.
(författare)
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Disentangling the Evidence of Milankovitch Forcing From Tree-Ring and Sedimentary Records
- 2022
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Ingår i: Frontiers in Earth Science. - : Frontiers Media SA. - 2296-6463. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- Tree-ring records constitute excellent high-resolution data and provide valuable information for climate science and paleoclimatology. Tree-ring reconstructions of past temperature variations agree to show evidence for annual-to-centennial anomalies in past climate and place the industrial-era warming in the context of the late Holocene climate patterns and regimes. Despite their wide use in paleoclimate research, however, tree rings have also been deemed unsuitable as low-frequency indicators of past climate. The arising debate concerns whether the millennia-long tree-ring records show signals of orbital forcing due to the Milankovitch cycles. Here, we produce a summer-temperature reconstruction from tree-ring chronology running through mid- and late-Holocene times (since 5486 BCE) comprising minimum blue channel light intensity (BI). The BI reconstruction correlates with existing and new tree-ring chronologies built from maximum latewood density (MXD) and, unlike the MXD data, shows temperature trends on Milankovitch scales comparable to various types of sedimentary proxy across the circumpolar Arctic. Our results demonstrate an unrevealed potential of novel, unconventional tree-ring variables to contribute to geoscience and climate research by their capability to provide paleoclimate estimates from inter-annual scales up to those relevant to orbital forcing.
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| 3. |
- Rutgersson, Anna, et al.
(författare)
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Recent Change - Atmosphere
- 2015
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Ingår i: Second Assessment of Climate Change for the Baltic Sea Basin. - Cham : Springer. - 9783319160061 - 9783319160054 ; , s. 69-97
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Bokkapitel (refereegranskat)abstract
- This chapter describes observed changes in atmospheric conditions in the Baltic Sea drainage basin over the past 200-300 years. The Baltic Sea area is relatively unique with a dense observational network covering an extended time period. Data analysis covers an early period with sparse and relatively uncertain measurements, a period with well-developed synoptic stations, and a final period with 30+ years of satellite data and sounding systems. The atmospheric circulation in the European/Atlantic sector has an important role in the regional climate of the Baltic Sea basin, especially the North Atlantic Oscillation. Warming has been observed, particularly in spring, and has been stronger in the northern regions. There has been a northward shift in storm tracks, as well as increased cyclonic activity in recent decades and an increased persistence of weather types. There are no long-term trends in annual wind statistics since the nineteenth century, but much variation at the (multi-)decadal timescale. There are also no long-term trends in precipitation, but an indication of longer precipitation periods and possibly an increased risk of extreme precipitation events.
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| 4. |
- Siddiqui, Tauseef, et al.
(författare)
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Broadband Transponder Based on Frequency-Reconfigurable Cluster Antenna and Phased Modulators
- 2020
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Ingår i: IEEE Antennas and Wireless Propagation Letters. - 1548-5757 .- 1536-1225. ; 19:2, s. 238-242
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Tidskriftsartikel (refereegranskat)abstract
- This letter presents a new concept of broadband transponder based on frequency-reconfigurable cluster antenna and phase-variable modulators. The transponder in this concept has multiport antenna, whose elements have strong mutual coupling between them. The technique presented in this concept takes advantage of the coupling between the antenna elements instead of avoiding it. By properly weighting the phases of the modulated signals in each port, the backscattered received power can be maximized. The weighting is done differently for different sets of frequencies to achieve instantaneous bandwidth over the frequency band of interest. © 2002-2011 IEEE.
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| 5. |
- Siddiqui, Tauseef, et al.
(författare)
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Concept of Beam Steerable Transponder based on Load Modulation
- 2020
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Ingår i: 2020 14th European Conference on Antennas and Propagation (EuCAP). - 9788831299008 ; , s. 1-5
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Konferensbidrag (refereegranskat)abstract
- The concept of beam steering transponder based on load modulation is proposed to enhance the received power of backscattered communication devices. The transponder consists of antenna array elements of equal length operates at the Wi-Fi frequency band of 2.4GHz. By properly weighting the modulated signal in each port, the received power can be maximized in a particular direction depending on the direction of arrival (DoA) of the signal. The weighting is done differently for each direction. It provides up to approximately 11dB improvement in received power with weighting compared to backscatter communication with a single antenna transponder. The concept is studied theoretically and by simulations.
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