| 651. |
- Nygren, Patrik, 1979-
(författare)
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De Novo Design and Characterization of Surface Binding Peptides - Steps toward Functional Surfaces
- 2006
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The ability to create surfaces with well-defined chemical properties is a major research field. One possibility to do this is to design peptides that bind with a specific secondary structure to silica nanoparticles. The peptides discussed in this thesis are constructed to be random coil in solution, but are “forced” to become helical when adsorbed to the particles. The positively charged side-chains on the peptides strongly disfavor an ordered structure in solution due to electrostatic repulsion. When the peptides are introduced to the particles these charges will strongly favor the structure because of ion pair bonding between the peptide and the negatively charged nanoparticles. The peptide-nanoparticle system has been thoroughly investigated by systematic variations of the side-chains. In order to determine which factors that contributes to the induced structure, several peptides with different amino acid sequences have been synthesized. Factors that have been investigated include 1) the positive charge density, 2) distribution of positive charges, 3) negative charge density, 4) increasing hydrophobicity, 5) peptide length, and 6) by incorporating amino acids with different helix propensities. Moreover, pH dependence and the effect of different nanoparticle curvature have also been investigated. It will also be shown that the system can be modified to incorporate a catalytic site that is only active when the helix is formed. This research will increase our understanding of peptide-surface interactions and might be of importance for both nanotechnology and medicine.
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| 652. |
- Nyholm Rattfelt, Jenny, et al.
(författare)
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Biodegradation kinetics of selected brominated flame retardants in aerobic and anaerobic soil
- 2010
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Ingår i: Environmental Pollution. - : Elsevier. - 0269-7491 .- 1873-6424. ; 158:6, s. 2235-2240
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Tidskriftsartikel (refereegranskat)abstract
- The purpose of the present study was to investigate the biodegradation kinetics in aerobic and anaerobic soil of the following brominated flame retardants: 2,4,4'-tribromodiphenyl ether (BDE 28), decabromodiphenyl ether (BDE 209), tetrabromobisphenol A (TBBPA), 1,2-dibromo-4-(1,2-dibromoethyl)cyclohexane (TBECH), 2,4,6-tribromophenol (246BrPh), and hexabromobenzene (HxBrBz). For comparison, the biodegradation of the chlorinated compounds 2,4,4'-trichlorodiphenyl ether (CDE 28), 2,4,6-trichlorophenol (246ClPh), hexachlorobenzene (HxClBz), and 2,2',4,4',5,5'-hexachlorobiphenyl (PCB 153) was also assessed. In aerobic soil, BDE 209 showed no significant degradation during the test period, but concentrations of the other BFRs declined, with half-lives decreasing in the following order: BDE 28 > TBBPA > TBECH > HxBrBz > 246BrPh. Declines in almost the same order were observed in anaerobic soil: BDE 28, BDE 209 > TBBPA > HxBrBz > TBECH >246BrPh. Intra- and extrapolated half-lives in soil of tested brominated flame retardants ranged from 7 days for 2,4,6-tribromorophenol to >400 days for decabromodiphenyl ether.
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| 653. |
- Nyholm Rattfelt, Jenny, et al.
(författare)
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Environmental occurrence of emerging and legacy brominated flame retardants near suspected sources in Norway
- 2013
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Ingår i: Science of the Total Environment. - : Elsevier. - 0048-9697 .- 1879-1026. ; 443, s. 307-314
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Tidskriftsartikel (refereegranskat)abstract
- The environmental occurrence of potentially emerging brominated flame retardants (BFRs) was investigated near suspected source zones in Norway, within seepage water, sewage waste water, sewage sludges, and sediments. Analyzed emerging BFRs included 1,2-dibromo-4-(1,2-dibromoethyl) cyclohexane (TBECH), 1,2-bis(2,4,6-tribromophenoxy) ethane (BTBPE), decabromodiphenylethane (DBDPE), ethylene bis(tetrabromophthalimide) (EBTPI), tetrabromobisphenol A diallyl ether (TBBPA AE), and tetrabromobisphenol A bis(2,3-dipropyl ether) (TBBPA DBPE). In addition selected polybrominated diphenylethers (PBDEs) were analyzed, so that findings could be compared to legacy BFRs. An analytical method based on liquid chromatography atmospheric pressure photoionization tandem mass spectrometry was developed for analysis of EBTPI, TBBPA AE, and TBBPA DBPE. The legacy BFRs were in general found in higher levels and abundances than the studied emerging BFRs. However, BTBPE was detected in most of the studied matrices (sewage sludge, seepage water and sediment). DBDPE was detected in sewage sludge, waste water, seepage water and in sediment taken close to a combined metal recycling and car dismantling site. TBECH was found in seepage water, waste water and sewage sludge. EBTPI was identified in one seepage water sample; TBBPA AE was detected both in seepage water and sediment, and TBPPA DBPE in waste water and seepage water. Of the emerging BFRs, the highest levels in water samples were quantified for TBBPA DBPE (81ng/L, seepage water from a combined metal recycling and car dismantling site) and in sediment for BTBPE (6.5ng/g, taken close to landfill). The findings of current-use BFRs in seepage water, sediment and in sewage suggest that further investigations are needed of the environmental fate and effects of these flame retardants.
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| 654. |
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| 655. |
- Olofson, K. Frans G., 1976, et al.
(författare)
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Rydberg Matter clusters of alkali metal atoms: the link between meteoritic matter, polar mesosphere summer echoes (PMSE), sporadic sodium layers, polar mesospheric clouds (PMCs, NLCs), and ion chemistry in the mesosphere
- 2010
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Ingår i: arXiv:1002.1570v1[astro-ph.EP].
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- There exists a material which links together the influx of meteoritic matter from interplanetary space, the polar mesosphere summer echoes (PMSE), the sporadic sodium layers, the polar mesospheric clouds (PMCs, NLCs), and the observed ion chemistry in the mesosphere. The evidence in these research fields is here analyzed and found to agree well with the properties of Rydberg Matter (RM). This material has been studied with numerous methods in the laboratory. Alkali atoms, mainly Na, reach the mesosphere in the form of interplanetary (meteoritic, cometary) dust. The planar RM clusters NaN usually contain N = 19, 37 or 61 atoms, and have the density of air at 90 km altitude where they float. The diameters of the clusters are 10-100 nm from laboratory high precision radio frequency spectroscopic studies. Such experiments show that RM clusters interact strongly with radar frequencies: this explains the radio frequency heating and reflection studies of PMSE layers. The clusters give circular polarized scattering and depolarized scattering of visible light in laboratory experiments: similar effects are observed in light scattering and lidar studies of NLCs. The clusters give the low temperature in the mesosphere by efficient selective radiation at long wavelengths, which is observed in RF emission experiments. The lowest possible stable temperature of the mesopause is calculated for the first time to be 121 K in agreement with measurements, based on the strong optical activity at long wavelengths in RM. Sporadic sodium layers are explained in a unique way as due to shockwaves in the RM layers. Due to the high electronic excitation energy in RM clusters, they induce efficient reactions forming ions of all atoms and molecules in the atmosphere thus providing condensation nuclei for water vapour. This finally gives the visible part of the PMC structure. Especially the sporadic sodium layers and the PMSE give direct evidence for the existence of RM layers at the mesopause. The present contribution fills the gap between and partially replaces the separate theories used to describe the various aspects of these intriguing phenomena.
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| 656. |
- Olofson, K. Frans G., 1976, et al.
(författare)
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Urban aerosol evolution and particle formation during wintertime temperature inversions
- 2009
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Ingår i: Atmospheric Environment. - : Elsevier BV. - 1352-2310. ; 43, s. 340-346
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Tidskriftsartikel (refereegranskat)abstract
- Aerosol temporal and spatial distributions during wintertime temperature inversions in Gothenburg, Sweden, have been characterized by ground-based and airborne particle measurements combined with lidar measurements. Ground inversions frequently developed during evenings and nights with stable cold conditions, and the low wintertime insolation often resulted in near neutral boundary layer conditions during day-time. Under these conditions ground level aerosol concentrations peaked during morning rush hours and often remained relatively high throughout the day due to inefficient ventilation. The particle number concentrations decreased slowly with increasing altitude within the boundary layer, and measurements slightly above the boundary layer suggested limited entrainment of polluted air into the free troposphere. High concentrations of ultrafine particles were observed throughout the boundary layer up to altitudes of 1100 m, which suggested that nucleation took place within the residual layer during the night and early morning. Recently formed particles were also observed around midday when the layer near ground was ventilated by mixing into the boundary layer, which indicated that ultrafine particles were either transported down from the residual layer to ground level or formed when the polluted surface layer mixed with the cleaner air above.
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| 657. |
- Ottosson, Patrik, et al.
(författare)
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An ultra-wideband system for measuring the dielectric properties of mineral compounds in a heat-reaction chamber at high temperatures
- 2023
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Ingår i: IEEE Transactions on Instrumentation and Measurement. - : IEEE. - 0018-9456 .- 1557-9662. ; 72
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Tidskriftsartikel (refereegranskat)abstract
- A measurement system for the measurement of microwave dielectric properties of mineral compounds at temperatures up to +1000°C is presented. It includes the simultaneous measurement of mass and temperature. Samples volumes in the range 0.01 to 0.1 m 3 can be studied. The system comprises a heat reaction chamber on a mass scale with mounted ultra-wideband (UWB) radio sensors and temperature probes. The complex refractive index is determined from the UWB signals using a technique with windowing to suppress interference and fitting of a modelled signal to the experimental ones. The developed method is validated by measuring the complex refractive index of water from +82°C down to +23°C and comparing with literature values. The systems is used to study calcination of limestone, i.e. the chemical decomposition of CaCO 3 to CaO and CO 2 when heated up to +1000°C. The chemical decomposition is clearly seen as a decrease in mass and as significant changes in the complex refractive index. The system could be used also for other mineral compounds and other types of materials.
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| 658. |
- Ottosson, Patrik, et al.
(författare)
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UWB Radio Measurement and Time-Domain Analysis of Anisotropy in Wood Chips
- 2018
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Ingår i: IEEE Sensors Journal. - 1530-437X .- 1558-1748. ; 18:22, s. 9112-9119
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Tidskriftsartikel (refereegranskat)abstract
- Ultra-wideband (UWB) radio transmission measurements have been used to determine the moisture content of wood chips using a time domain technique. Wood chips have been found to have birefringent dielectric properties acting as an anisotropic dielectric effective medium. Birefringence in wood chips occurs because of the orientation and the shape of wood chips, and microscopic structures of these objects, like wood fibers. The birefringence gives rise to two different wavefronts along the principal axes that have different dielectric properties. Each wavefront has a specific time-domain signal, that can be used to determine the moisture content. In industrial applications, for example in measurement on wood chips in trucks, the vertical polarization direction is the preferable polarization because this signal has higher signal-to-noise ratio (SNR), which makes the signal more identifiable at longer distance (2-3 m). Thus, UWB radio transmission measurement and time-domain analysis is a robust technology to investigate larger containers of wood chips and to determine the moisture content with high accuracy.
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| 659. |
-
Ovisshetens tid. Den nationella SOM-undersökningen 2022
- 2023
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Samlingsverk (redaktörskap) (övrigt vetenskapligt/konstnärligt)abstract
- Vi befinner oss i en ovisshetens tid. Säkerhetsläget i omvärlden har försämrats. Det rasar ett krig i Europas östligaste delar. Oron för nationens säkerhet har fått svenska politiker att bryta en tvåhundraårig tradition av alliansfrihet. Parallellt har energi- och matpriser rusat, boräntor höjts och inflationen stigit till den högsta nivån på trettio år. Det har väckt osäkerhet om den svenska ekonomins styrka och oro för den egna plånboken. Nationellt slogs rekord i dödligt skjutvapenvåld, med allt yngre gärningspersoner. Samhällets insatser tycks ständigt ligga steget efter och det råder oenighet om vilka de rätta insatserna är. I samband med 2022 års valrörelser fick frågan om kärnkraftens bevarande ny energi. Efter valet deklarerade den nytillträdda regeringen en ny riktning för svensk migrationspolitik. Ovisshet föder osäkerhet och oro. Samtidigt kan ovissheten leda till beslutsamhet när gamla sanningar ses i ett nytt ljus. Ovissheten har många nyanser. Ovisshetens tid är SOM-institutets 82:a forskarantologi. Utifrån 2022 års nationella SOM-undersökning – nummer 37 i ordningen – analyserar forskare från olika discipliner vid svenska universitet och högskolor de senaste årens samhällsutveckling. Bokens innehåll berör på många sätt den ovisshet som präglar Sverige inom områden som rör (S)amhället, (O)pinion och (M)edier.
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| 660. |
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