| 1. |
- Fryk, Emanuel, et al.
(författare)
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Microdialysis and proteomics of subcutaneous interstitial fluid reveals increased galectin-1 in type 2 diabetes patients
- 2016
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Ingår i: Metabolism-Clinical and Experimental. - : Elsevier BV. - 0026-0495 .- 1532-8600. ; 65:7, s. 998-1006
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Tidskriftsartikel (refereegranskat)abstract
- Objective. To identify a potential therapeutic target for type 2 diabetes by comparing the subcutaneous interstitial fluid from type 2 diabetes patients and healthy men. Methods. Proteomics was performed on the interstitial fluid of subcutaneous adipose tissue obtained by microdialysis from 7 type 2 diabetes patients and 8 healthy participants. 851 proteins were detected, of which 36 (including galectin-1) showed significantly altered expression in type 2 diabetes. We also measured galectin-1 expression in: (1) adipocytes isolated from adipose tissue biopsies from these participants; (2) subcutaneous adipose tissue of 24 obese participants before, during and after 16 weeks on a very low calorie diet (VLCD); and (3) adipocytes isolated from 6 healthy young participants after 4 weeks on a diet and lifestyle intervention to promote weight gain. We also determined the effect of galectin-1 on glucose uptake in human adipose tissue. Results. Galectin-1 protein levels were elevated in subcutaneous dialysates from type 2 diabetes compared with healthy controls (p < 0.05). In agreement, galectin-1 mRNA expression was increased in adipocytes from the type 2 diabetes patients (p < 0.05). Furthermore, galectin-1 mRNA expression was decreased in adipose tissue after VLCD (p < 0.05) and increased by overfeeding (p < 0.05). Co-incubation of isolated human adipocytes with galectin-1 reduced glucose uptake (p < 0.05) but this was independent of the insulin signal. Conclusion. Proteomics of the interstitial fluid in subcutaneous adipose tissue in vivo identified a novel adipokine, galectin-1, with a potential role in the pathophysiology of type 2 diabetes. (C) 2016 Elsevier Inc. All rights reserved.
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| 2. |
- Antoni, Per, et al.
(författare)
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Europium confined cyclen dendrimers with photophysically active triazoles
- 2008
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Ingår i: Journal of Materials Chemistry. - : Royal Society of Chemistry (RSC). - 0959-9428 .- 1364-5501. ; 18:22, s. 2545-2554
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Tidskriftsartikel (refereegranskat)abstract
- Dendrimers up to the fourth generation (G1-G4) were successfully synthesized via the efficient copper catalyzed 1,3-dipolar cycloaddition between primary alkynes and azides (CuAAC), also referred to as a click reaction. The synthetic protocol involved the preparation of presynthesized dendron wedges that subsequently were attached to a tetra-valent alkyne functional cyclen core. These constructed structures integrated stable triazole groups "intra-locked'' between the cyclen and dendron wedges. The incorporation of a lanthanide metal ion, europium, into the interior of all cyclen dendrimers was monitored by FT-IR. Interestingly, the photophysical results showed that the proximate triazole not only acts as a stable linker but also as a sensitizers, transferring its singlet-singlet excitation in the ultraviolet region (270-290 nm) to the partially filled luminescent lanthanide 4f shell. An increase of luminescence decay time from the lanthanide D-5(0) -> F-7(2) emission was observed with increasing dendrimer size, indicating that the shielding effect of the dendron wedges is important for the relaxation of the photo-excitation and energy transfer. To the best of our knowledge, this is the first time a set of dendron wedges have successfully been attached to a cyclen metal ion cage via the versatile click reaction. Furthermore, the produced triazoles intra-locked in close proximity to the macrocycle core elucidated an interesting photophysical function.
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| 3. |
- Berglund, Olof, et al.
(författare)
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Persistent organic pollutants in river food webs: influence of trophic position and degree of heterotrophy
- 2005
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - 1205-7533. ; 62:9, s. 2021-2032
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Tidskriftsartikel (refereegranskat)abstract
- We investigated how the degree of autotrophy/heterotrophy and organism trophic position influenced the bioaccumulation of polychlorinated biphenyls (PCBs) in 10 benthic river food webs consisting of terrestrial detritus, periphyton, invertebrates, and age-0 brown trout (Salmo trutta) in southern Sweden. Concentrations of PCBs increased with trophic position, estimated from delta(15)N and delta(13)C, on a dry weight basis (ng center dot g(-1) dry weight) but not on a lipid weight basis (ng center dot g(-1) lipid). PCB biomagnification factors between the first and second trophic levels (invertebrates/ periphyton and invertebrates/detritus) ranged between 0.3 and 2.3 and between the second and third levels (trout/invertebrates) between 0.3 and 2.0 on a lipid weight basis. The mean proportion of carbon ultimately derived from terrestrial sources, alpha, was 0.82 +/- 0.19 for invertebrates and 0.67 +/- 0.28 for trout. Contrary to our hypothesis, PCB concentrations in trout were positively related to alpha (r(2) = 0.58-0.77, p < 0.05). As alpha and the periphyton density (g C center dot m(-2)) in the rivers was positively related (r(2) = 0.88, p < 0.01), we propose that this relationship was due to an increased retention and exposure of PCBs to trout in rivers with low grazing pressure and high periphyton density.
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| 4. |
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| 5. |
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| 6. |
- Hansson, Lars-Anders, et al.
(författare)
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Consumption patterns, complexity and enrichment in aquatic food chains
- 1998
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 265:1399, s. 901-906
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Tidskriftsartikel (refereegranskat)abstract
- The interactions between consumers and prey, and their impact on biomass distribution among trophic levels, are central issues in both empirical and theoretical ecology. In a long-term experiment, where all organisms, including the top predator, were allowed to respond to environmental conditions by reproduction, we tested predictions from `prey-dependent' and `ratio-dependent' models. Prey-dependent models made correct predictions only in the presence of strong interactors in simple food chains, but failed to predict patterns in more complex situations. Processes such as omnivory, consumer excretion, and unsuitable prey-size windows (invulnerable prey) increased the complexity and created patterns resembling ratio-dependent consumption. However, whereas the prey-dependent patterns were created by the mechanisms predicted by the model, ratio-dependent patterns were not, suggesting that they may be right for the wrong reason'. We show here that despite the enormous complexity of ecosystems, it is possible to identify and disentangle mechanisms responsible for observed patterns in community structure, as well as in biomass development of organisms ranging in size from bacteria to fish.
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| 7. |
- Holmqvist, Niklas, et al.
(författare)
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Lake trophic status and bioaccumulation of polychlorinated biphenyls in benthic organisms: a comparison between littoral and profundal invertebrates
- 2005
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Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - 1205-7533. ; 62:6, s. 1201-1209
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the influence of lake trophic status on accumulation of polychlorinated biphenyls (PCBs) in littoral and profundal invertebrates from 19 lakes in southern Sweden. The PCB concentration in profundal chironomids (Chironomus sp.) was negatively correlated with lake trophy but the concentration in littoral crayfish (Pacifasticus leniusculus) was unrelated to shifting nutrient regimes. PCB concentrations in chironomids were negatively correlated, while crayfish did not correlate with lake total phosphorus. Two findings indicate that different processes determine bioaccumulation in littoral and profundal invertebrates: (i) a lack of correlation between PCB concentrations in crayfish and chironomids within lakes and (ii) some differences in congener distribution in the two species. We suggest a possible explanation in that chironomids are directly exposed to settling material from the pelagic zone, while crayfish are omnivorous and feed mainly in the littoral zone. A intensive investigation on one pond population could not reveal any individual factors, such as lipid content, size, or sex, influencing bioaccumulation of PCBs in crayfish.
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| 8. |
- Holmqvist, Niklas, et al.
(författare)
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Low levels of persistent organic pollutants (POPS) in New Zealand eels reflect isolation from atmospheric sources
- 2006
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Ingår i: Environmental Pollution. - : Elsevier BV. - 0269-7491. ; 141:3, s. 532-538
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Tidskriftsartikel (refereegranskat)abstract
- Polychlorinated biphenyls (PCBs) and organic pesticides (i.e., DDTs) were measured in long finned eels (Anguilla dieffenbachii) in 17 streams on the west coast of South Island, New Zealand. Very low levels of PCBs and low levels of ppDDE were found. The concentrations of PCBs and ppDDE were not correlated within sites indicating that different processes determined the levels of the two pollutants in New Zealand eels. The PCBs probably originate from atmospheric transport, ppDDE levels are determined by land use and are higher in agriculture areas. The low contamination level of these aquatic systems seems to be a function of a low input from both long and short-range transport as well as few local point sources. No correlation could be found between lipid content and persistent organic pollutants (POPs) concentration (as shown in previous studies) in the eels which could be explained by low and irregular intake of the pollutants.
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| 9. |
- Holmqvist, Niklas, et al.
(författare)
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Persistent organic pollutants (POP) in a benthic omnivore - A comparison between lake and stream crayfish populations
- 2007
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Ingår i: Chemosphere. - : Elsevier BV. - 1879-1298 .- 0045-6535. ; 66:6, s. 1070-1078
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Tidskriftsartikel (refereegranskat)abstract
- We investigated the accumulation of PCB and DDT in crayfish populations in 10 streams in southern Sweden. The results were compared with an earlier study on crayfish in lakes from the same area. We found that the concentration of pollutants in crayfish did not differ between the two types of systems. Variation in body burden was higher in stream living crayfish probably because of the higher influence from pollutants deposited in the catchment area and the more dynamic transport in streams. In streams, pp'-DDE concentrations were positively correlated to trophic status (total phosphorous) while PCB did not show any correlation with the nutrient regime. Further, mean Sigma PCB and p,p'-DDE concentrations in crayfish did not correlate in streams. We suggest that the sources of the two pollutants differ for stream living crayfish. The results indicate that crayfish in streams are affected to a higher degree to pollutants in the catchment area and the precipitation regime. In lakes, internal processes govern uptake of pollutants in crayfish.
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| 10. |
- Jephson, Therese, et al.
(författare)
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Trophic interactions in Zostera marina beds along the Swedish coast
- 2008
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Ingår i: Marine Ecology - Progress Series. - : Inter-Research Science Center. - 1616-1599 .- 0171-8630. ; 369, s. 63-76
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Tidskriftsartikel (refereegranskat)abstract
- We compared eelgrass Zostera marina communities in 3 regions in Sweden believed to be affected by eutrophication and overfishing, to determine whether bottom-up or top-down processes control the biomass of epiphytic macroalgae and grazers. Nitrogen and carbon isotope signatures were analyzed to explore the food webs and to identify the grazing species feeding on filamentous algae and/or eelgrass. Mixing model (IsoSource version 1.3.1) analysis of the isotope signatures indicated that the amphipods Gammarus locusta and Microdeutopus gryllotalpa fed primarily on filamentous algae and that only 2 small gastropod species consumed eelgrass. Moreover, the grass shrimp Palaemon elegans and F adspersus were ca. 1 trophic level above amphipods and algae, but according to the mixing model played different trophic roles in the different areas. The highest biomass of filamentous algae was found in the west coast beds housing grazers with the lowest biomass and mean size (predominantly G. locusta and M. gryllotalpa, 0.5 to 3 mm). In contrast, the Baltic Sea beds had low algal biomass, but the grazers (mostly G. locusta and Idotea baltica) had higher biomass and were significantly larger (mean size ca. 10 mm). An overall negative correlation was found between grazer biomass and biomass of filamentous algae. The significantly smaller grazers and absence of isopod grazers on the west coast may be due to substantial consumption by small predatory fish. This supports the suggestions that, in Swedish eelgrass beds, grazers are top-down controlled, and overexploitation. of large predators and eutrophication play an important role in the recent increases in algal biomass.
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| 11. |
- Kotta, Jonne, et al.
(författare)
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Cleaning up seas using blue growth initiatives: Mussel farming for eutrophication control in the Baltic Sea
- 2020
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Ingår i: Science of the Total Environment. - : Elsevier BV. - 0048-9697 .- 1879-1026. ; 709
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Tidskriftsartikel (refereegranskat)abstract
- © 2019 The Authors Eutrophication is a serious threat to aquatic ecosystems globally with pronounced negative effects in the Baltic and other semi-enclosed estuaries and regional seas, where algal growth associated with excess nutrients causes widespread oxygen free “dead zones” and other threats to sustainability. Decades of policy initiatives to reduce external (land-based and atmospheric) nutrient loads have so far failed to control Baltic Sea eutrophication, which is compounded by significant internal release of legacy phosphorus (P) and biological nitrogen (N) fixation. Farming and harvesting of the native mussel species (Mytilus edulis/trossulus) is a promising internal measure for eutrophication control in the brackish Baltic Sea. Mussels from the more saline outer Baltic had higher N and P content than those from either the inner or central Baltic. Despite their relatively low nutrient content, harvesting farmed mussels from the central Baltic can be a cost-effective complement to land-based measures needed to reach eutrophication status targets and is an important contributor to circularity. Cost effectiveness of nutrient removal is more dependent on farm type than mussel nutrient content, suggesting the need for additional development of farm technology. Furthermore, current regulations are not sufficiently conducive to implementation of internal measures, and may constitute a bottleneck for reaching eutrophication status targets in the Baltic Sea and elsewhere.
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| 12. |
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| 13. |
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| 14. |
- Larsson, Per, et al.
(författare)
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Heavy metals and stable isotopes in a benthic omnivore in a trophic gradient of lakes
- 2007
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Ingår i: Environmental Science & Technology. - : American Chemical Society (ACS). - 1520-5851 .- 0013-936X. ; 41:17, s. 5973-5979
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Tidskriftsartikel (refereegranskat)abstract
- Heavy metals (Cd, Hg, and Pb) and stable isotopes (N-15, C-13) in crayfish (Pacifastacus leniusculus) were studied in a trophic gradient of lakes (N = 19) in southern Sweden. Trophic indicators of the lakes as total phosphorus (tot-P) varied from 5 to 93 mu g/L. The examined lakes had no known point sources of heavy metals, but the catchment areas varied from mainly forested to agricultural land. Cd and Hg in crayfish were affected by the trophic status of the lakes, showing significant negative relationship with tot-P, total nitrogen, and chlorophyll A content and a positive relationship with lake transparency (Secchi depth). The concentration of these two heavy metals was thus higher in crayfish in the oligotrophic lakes and decreased linearly to the eutrophic ones. Pb was not related to any lake variable. Stable isotopes of carbon (delta C-13) and nitrogen (615N) in crayfish were a reflection of that found in the sediment as shown by positive linear relationships for the lakes. In the sediment of the lakes, delta C-13 signature showed significant negative relationships with the trophic indicators but positive results were shown for lake transparency. The trophic gradient of the lakes was reflected by delta C-13 in the sediment and in the crayfish. 615N in crayfish was a reflection of 615N in the sediment but the relationship was not coupled to the trophic statue of the lakes. The results from the study show that Cd and Hg in benthic omnivores as crayfish are affected by ecological processes in lakes, such as eutrophication. Stable isotopes, such as 13C and 15 N, can be used to study these ecological processes.
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| 15. |
- Lindblom, Per, 1974, et al.
(författare)
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Endothelial PDGF-B retention is required for proper investment of pericytes in the microvessel wall.
- 2003
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Ingår i: Genes & development. - : Cold Spring Harbor Laboratory. - 0890-9369 .- 1549-5477. ; 17:15, s. 1835-40
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Tidskriftsartikel (refereegranskat)abstract
- Several platelet-derived growth factor (PDGF) and vascular endothelial growth factor (VEGF) family members display C-terminal protein motifs that confer retention of the secreted factors within the pericellular space. To address the role of PDGF-B retention in vivo, we deleted the retention motif by gene targeting in mice. This resulted in defective investment of pericytes in the microvessel wall and delayed formation of the renal glomerulus mesangium. Long-term effects of lack of PDGF-B retention included severe retinal deterioration, glomerulosclerosis, and proteinuria. We conclude that retention of PDGF-B in microvessels is essential for proper recruitment and organization of pericytes and for renal and retinal function in adult mice.
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| 16. |
- Nyström, Andreas, et al.
(författare)
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Characterization of Poly(norbornene) Dendronized Polymers Prepared by Ring-Opening Metathesis Polymerization of Dendron Bearing Monomers
- 2006
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 39:21, s. 7241-7249
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Tidskriftsartikel (refereegranskat)abstract
- The preparation and characterization of a series of first to fourth generation dendronized poly-(norbornene)s are presented. The monomers were synthesized in a divergent fashion from 5-norbornene-2-methanol, utilizing the acetonide protected anhydride of 2,2-bis(methylol)propionic acid. The norbornenyl bearing dendrons were polymerized by ring-opening metathesis polymerization, and it was found that the Grubbs' first generation catalyst resulted in polymers with lower polydispersity compared to the materials obtained when employing the second generation catalyst. Two series of first to fourth generation polymers were characterized by DSC, SEC, and dynamic rheological measurements. In addition, it was found that the fourth generation material could form regular, porous membranes and birefringent fibers. The membranes were characterized with atomic force and optical microscopy. The birefringent fibers were analyzed with X-ray diffraction, polarized FTIR, and polarized optical microscopy.
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| 17. |
- Nyström, Per, et al.
(författare)
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Crayfish in lakes and streams: individual and population responses to predation, productivity and substratum availability
- 2006
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Ingår i: Freshwater Biology. - : Wiley. - 0046-5070 .- 1365-2427. ; 51:11, s. 2096-2113
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Tidskriftsartikel (refereegranskat)abstract
- 1. In a correlative study, we investigated the relative importance of fish predation, refuge availability and resource supply in determining the abundance and size distributions of the introduced and omnivorous signal crayfish (Pacifastacus leniusculus) in lakes and streams. Moreover, the biomass and food selection of predatory fish was estimated in each habitat type and stable isotopes of carbon and nitrogen were measured in perch (Perca fluviatilis), the dominant predator in the lakes, and in its potential food sources (crayfish, juvenile roach and isopods). 2. In lakes, crayfish were the most frequent prey in large perch (46%), followed by other macroinvertebrates (26%, including the isopod Asellus aquaticus) and small fish (25%). Crayfish and fish dominated the gut contents of large perch with respect to biomass. Nitrogen signatures showed that perch were one trophic level above crayfish (approx. 3.4 parts per thousand) and a two-source mixing model using nitrogen isotope values indicated that crayfish (81%) contributed significantly more to perch isotope values than did juvenile roach (19%). A positive correlation was found between the abundance of crayfish and the biomass of large perch. Crayfish abundance in lakes was also positively correlated with the proportion of cobbles in the littoral zone. Lake productivity (chlorophyll a) was positively correlated with crayfish size, but not with crayfish abundance. 3. In streams, brown trout (Salmo trutta) were the most abundant predatory fish. Gut contents of large trout in a forested stream showed that terrestrial insects were the most frequently found prey (60%), followed by small crayfish (27%) and isopods (27%). In contrast to lakes, the relative abundance of crayfish was negatively correlated with the total biomass of predatory fish and with total biomass of trout. However, abundance of crayfish at sites with a low biomass of predatory fish varied considerably and was related to substratum grain size, with fewer crayfish being caught when the substratum was sandy or dominated by large boulders. The mean size of crayfish was greater at stream sites with a high standing stock of periphyton, but neither predator biomass nor substratum grain size was correlated with crayfish size. 4. Our results suggest that bottom-up processes influence crayfish size in lakes and streams independent of predator biomass and substratum availability. However, bottom-up processes do not influence crayfish abundance. Instead, substratum availability (lakes) and interactions between predation and substratum grain size (streams) need to be considered in order to predict crayfish abundance.
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| 18. |
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| 19. |
- Nyström Sandman, Antonia, et al.
(författare)
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Grön infrastruktur i havet : landskapsperspektiv i förvaltningen av Sveriges marina områden
- 2020
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- En kartläggning av havets naturkvaliteter har påbörjats genom arbetet med grön infrastruktur. Rapporten undersöker olika scenarier för hur den marina gröna infrastrukturen påverkas av mänskliga aktiviteter i förhållande till olika strategier för förvaltning. Projektet har genomfört tre fallstudier med olika fokus: strandexploatering, trålfiske och klimatförändring. Genom scenariobaserade analyser visar forskarna vilken effekt olika beslut och åtgärder kan få på naturskydds- och miljömål.Det tvärvetenskapliga projektet är ett samarbete mellan experter inom ekologi och juridik. Forskarna beskriver hur lagstiftning, planering och förvaltningsstrategier bör utformas och fungera ihop, och presenterar förslag för att stärka skyddet av den gröna infrastrukturen i Sveriges havsområden.Forskningen har finansierats av Naturvårdsverkets miljöforskningsanslag till stöd för Naturvårdsverket och Havs- och vattenmyndighetens verksamhet.
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| 20. |
- Parvin, Farjana, et al.
(författare)
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Divergent Age-Dependent Conformational Rearrangement within Aβ Amyloid Deposits in APP23, APPPS1, and AppNL-F Mice
- 2024
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Ingår i: ACS Chemical Neuroscience. - : AMER CHEMICAL SOC. - 1948-7193. ; 15:10, s. 2058-2069
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Tidskriftsartikel (refereegranskat)abstract
- Amyloid plaques composed of fibrils of misfolded A beta peptides are pathological hallmarks of Alzheimer's disease (AD). A beta fibrils are polymorphic in their tertiary and quaternary molecular structures. This structural polymorphism may carry different pathologic potencies and can putatively contribute to clinical phenotypes of AD. Therefore, mapping of structural polymorphism of A beta fibrils and structural evolution over time is valuable to understanding disease mechanisms. Here, we investigated how A beta fibril structures in situ differ in A beta plaque of different mouse models expressing familial mutations in the A beta PP gene. We imaged frozen brains with a combination of conformation-sensitive luminescent conjugated oligothiophene (LCO) ligands and A beta-specific antibodies. LCO fluorescence mapping revealed that mouse models APP23, APPPS1, and App(NL-F) have different fibril structures within A beta-amyloid plaques depending on the A beta PP-processing genotype. Co-staining with A beta-specific antibodies showed that individual plaques from APP23 mice expressing A beta PP Swedish mutation have two distinct fibril polymorph regions of core and corona. The plaque core is predominantly composed of compact A beta 40 fibrils, and the corona region is dominated by diffusely packed A beta 40 fibrils. Conversely, the A beta PP knock-in mouse App(NL-F), expressing the A beta PP Iberian mutation along with Swedish mutation has tiny, cored plaques consisting mainly of compact A beta 42 fibrils, vastly different from APP23 even at elevated age up to 21 months. Age-dependent polymorph rearrangement of plaque cores observed for APP23 and APPPS1 mice >12 months, appears strongly promoted by A beta 40 and was hence minuscule in App(NL-F). These structural studies of amyloid plaques in situ can map disease-relevant fibril polymorph distributions to guide the design of diagnostic and therapeutic molecules.
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| 21. |
- Persson, Anders, et al.
(författare)
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Effects of enrichment on simple aquatic food webs
- 2001
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Ingår i: American Naturalist. - : University of Chicago Press. - 0003-0147 .- 1537-5323. ; 157:6, s. 654-669
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Tidskriftsartikel (refereegranskat)abstract
- Simple models, based on Lotka-Volterra types of interactions between predator and prey, predict that enrichment will have a destabilizing effect on populations and that equilibrium population densities will change at the top trophic level and every second level below. We experimentally tested these predictions in three aquatic food web configurations subjected to either high or low nutrient additions. The results were structured by viewing the systems as either food chains or webs and showed that trophic level biomass increased with enrichment, which contradicts food chain theory. However, within each trophic level, food web configuration affected the extent to which different functional groups responded to enrichment. By dividing trophic levels into functional groups, based on vulnerability to consumption, we were able to identify significant effects that were obscured when systems were viewed as food chains. The results support the prediction that invulnerable prey may stabilize trophic-level dynamics by replacing other, more vulnerable prey. Furthermore, the vulnerable prey, such as Daphnia and edible algae, responded as predicted by the paradox of enrichment hypothesis; that is, variability in population density increased with enrichment. Hence, by describing ecosystems as a matrix of food web interactions, and by recognizing the interplay between interspecific competition and predation, a more complete description of the ecosystem function was obtained compared to when species were placed into distinct trophic levels.
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| 22. |
- Persson, Anders, et al.
(författare)
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Effects of enrichment on simple aquatic food webs
- 2001
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Ingår i: The American Naturalist. ; 157:6, s. 654-669
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Tidskriftsartikel (refereegranskat)abstract
- Simple models, based on Lotka-Volterra types of interactions between predator and prey, predict that enrichment will have a destabilizing effect on
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| 23. |
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| 24. |
- Shovsky, Alexander, et al.
(författare)
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Cationic poly(N -isopropylacrylamide) block copolymer adsorption investigated by dual polarization interferometry and lattice mean-field theory
- 2012
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Ingår i: Langmuir. - : American Chemical Society (ACS). - 0743-7463 .- 1520-5827. ; 28:39, s. 14028-14038
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Tidskriftsartikel (refereegranskat)abstract
- A series of cationic diblock copolymers, poly(N-isopropylacrylamide) 48-block-poly((3-acrylamidopropyl)trimethylammonium chloride) X, abbreviated as PNIPAAM48-b-PAMPTMA+ X (X = 0, 6, 10, 14, and 20), has been synthesized, and their adsorption onto silicon oxynitride from aqueous solution has been investigated using dual polarization interferometry. The polymer adsorption was modeled by using a lattice mean-field theory, and a satisfactory consistency between theory and experiments was found in terms of surface excess and layer thickness. Both theory and experiments show that the adsorption is limited by steric repulsion for X < Xmax and by electrostatic interactions for X > X max. Modeling demonstrates that significant surface charge regulation occurs due to adsorption. Both the nonionic and cationic block exhibit nonelectrostatic affinity to silicon oxynitride and thus contribute to the driving force for adsorption, and modeling is used for clarifying how changes in the nonelectrostatic affinity affects the surface excess. The segments of the nonionic and cationic blocks seem less segregated when both have a nonelectrostatic affinity for the surface compared to the case where the segments had no surface affinity. Adsorption kinetics was investigated experimentally. Two kinetic regimes were observed: the adsorption rate is initially controlled by the mass transfer rate to the surface and at higher coverage is limited by the attachment rate.
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| 25. |
- Stenroth, Patrik, et al.
(författare)
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Stable isotopes as an indicator of diet in omnivorous crayfish (Pacifastacus leniusculus): the influence of tissue, sample treatment, and season
- 2006
-
Ingår i: Canadian Journal of Fisheries and Aquatic Sciences. - 1205-7533. ; 63:4, s. 821-831
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Tidskriftsartikel (refereegranskat)abstract
- Stable isotopes have been used to analyse food webs and (or) trace movements of animals for about 30 years. There has been some debate on the use of different tissues and treatments before isotope analysis, as well as on seasonal effects. We found different crayfish (Pacifastacus leniusculus) tissues (muscle, hepatopancreas, exoskeleton, gill, and whole body) to have different isotope values. Lipid extraction made whole-body carbon isotope values higher but had no effect on nitrogen isotope values. Acidification made whole-body isotope values lower. For crayfish, there was no seasonal or interannual variation in isotope values. In contrast to studies based on gut content analysis, we found adult crayfish to be at least as carnivorous as young-of-the-year crayfish. Earlier studies often have assumed that each food source contributes both nitrogen and carbon in equal proportions. Omnivores do not fit easily into this view. We suggest that nitrogen and carbon in an organism could come from different sources. Adopting this view for a pond food web could render crayfish both predators and detritivores as crayfish prey on nitrogen sources (other invertebrates) and consume large amounts of detritus to satisfy their carbon demand.
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