| 1. |
- Darracq, Amelie, et al.
(författare)
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Quantification of advective solute travel times and mass transport through hydrological catchments
- 2010
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Ingår i: Environmental Fluid Mechanics. - : Springer Science and Business Media LLC. - 1567-7419 .- 1573-1510. ; 10:1-2, s. 103-120
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Tidskriftsartikel (refereegranskat)abstract
- This study has investigated and outlined the possible quantification and mapping of the distributions of advective solute travel times through hydrological catchments. These distributions are essential for understanding how local water flow and solute transport and attenuation processes affect the catchment-scale transport of solute, for instance with regard to biogeochemical cycling, contamination persistence and water quality. The spatial and statistical distributions of advective travel times have been quantified based on reported hydrological flow and mass-transport modeling results for two coastal Swedish catchments. The results show that the combined travel time distributions for the groundwater-stream network continuum in these catchments depend largely on the groundwater system and model representation, in particular regarding the spatial variability of groundwater hydraulic parameters (conductivity, porosity and gradient), and the possible contributions of slower/deeper groundwater flow components. Model assumptions about the spatial variability of groundwater hydraulic properties can thus greatly affect model results of catchment-scale solute spreading. The importance of advective travel time variability for the total mass delivery of naturally attenuated solute (tracer, nutrient, pollutant) from a catchment to its downstream water recipient depends on the product of catchment-average physical travel time and attenuation rate.
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| 2. |
- Darracq, Amelie, et al.
(författare)
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Scale and model resolution effects on the distributions of advective solute travel times in catchments
- 2010
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Ingår i: Hydrological Processes. - : John Wiley & Sons, Ltd.. - 0885-6087 .- 1099-1085. ; 24:12, s. 1697-1710
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Tidskriftsartikel (refereegranskat)abstract
- Advective solute travel times and their distributions in hydrological catchments are useful descriptors of the dynamics and variation of the physical mass transport among and along the different source-to-recipient pathways of solute transport through the catchments. This article investigates the scale dependence and the effects of model and data resolution on the quantification of advective travel times and their distributions in the Swedish catchment areas of Norrström and Forsmark. In the surface water networks of the investigated (sub)catchments, the mean advective travel time increases with (sub)catchment scale, whereas the relative travel time variability around the mean value (coefficient of variation, CV) is scale-invariant and insensitive to model resolution. In the groundwater and for the whole (sub)catchments, both the mean value and the CV of travel times are scale-invariant, but sensitive to model resolution and accuracy. Such quantifications and results of advective travel times constitute important steps in the development of improved understanding and modelling of nutrient, pollutant and tracer transport through catchments.
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| 3. |
- Destouni, Georgia, et al.
(författare)
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Lagrangian pathway-travel time theory and scenario analysis of tracer-pollutant and uncertainty propagation through catchments
- 2012
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Ingår i: Geophysical Research Abstracts, Vol. 14, EGU2012-6940, 2012.
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Konferensbidrag (refereegranskat)abstract
- This paper presents how tracer, nutrient and pollutant transport through a catchment can be analyzed based on mean flow and other flow-transport properties given or resolved by simulations, by following the trajectories (pathways) of transport through the catchment and the flow-transport property distribution among them. Convolution of relevant property distributions across consecutive hydrological units, aggregated over the trajectories that originate from the tracer/pollutant-specific injection area, captures hydrological dispersion with its basic measure derived as the travel time coefficient of variation. Various memory functions can be introduced in a relatively simple manner for incorporating retention/mass transfer mechanisms under conditions of statistical stationarity. The paper further shows how spatial and temporal flow variability can be accounted for in this general theory, and how each and both of these variability components influence hydrological transport in catchments. Moreover, the paper outlines how the theory can be used in a scenario analysis approach to quantify and map the effects of uncertainty in physical and biogeochemical characteristics on diffuse hydrological transport and its uncertainty
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| 4. |
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| 5. |
- Hevekerl, Heike, 1982-, et al.
(författare)
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Dark states in ionic oligothiophene bioprobes-evidence from fluorescence correlation spectroscopy and dynamic light scattering
- 2014
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 118:22, s. 5924--5933
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Tidskriftsartikel (refereegranskat)abstract
- Luminescent conjugated polyelectrolytes (LCPs) can upon interaction with biological macromolecules change their luminescent properties, and thereby serve as conformation- and interaction-sensitive biomolecular probes. However, to exploit this in a more quantitative manner, there is a need to better understand the photophysical processes involved. We report studies of the conjugated pentameric oligothiophene, derivative p-FTAA, which changes optical properties with different p-FTAA concentrations in aqueous buffers, and in a pH and oxygen saturation dependent manner. Using dynamic light scattering, luminescence spectroscopy and fluorescence correlation spectroscopy, we find evidence for a monomer dimer equilibrium, for the formation of large clusters of p-FTAA in aqueous environment, and can couple aggregation to changed emission properties of oligothiophenes. In addition, we observe the presence of at least two dark transient states, one presumably being a triplet state. Oxygen was found to statically quench the p-FTAA fluorescence but also to promote molecular fluorescence by quenching dark transient states of the p-FTAA molecules. Taken together, this study provides knowledge of fluorescence and photophysical features essential for applying p-FTAA and other oligothiophene derivatives for diagnostic purposes, including detection and staining of amyloid aggregates.
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| 6. |
- Ijumba, Petrida, 1951-
(författare)
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Intervention for improved newborn feeding and survival where HIV is common : Perceptions and effects of a community-based package for maternal and newborn care in a South African township
- 2014
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- South Africa recently changed infant feeding policy within Prevention of Mother to Child Transmission (PMTCT) of HIV from free formula to recommendation of breastfeeding for all. The country is evaluating the role of Community Health Workers (CHWs) in supporting mothers and newborns.The aim of this thesis is to explore perceptions of household members on the value given to and the social forces behind formula feeding in light of the recent policy change, and to assess the effect of a community-based package of maternal and newborn care delivered by CHWs on HIV-free survival and exclusive and appropriate infant feeding up to 12 weeks of age.Studies were conducted in a high HIV prevalence township. Focus group discussions were performed (grandmothers, fathers and teenage mothers) and in-depth interviews with HIV-positive and HIV-negative mothers. Perceptions of household members on the formula policy change were explored and the value household members place on formula feeding and circumstances that drive it. In a cluster-randomized trial (15 intervention, 15 control clusters) CHWs provided two antenatal and five post-natal home visits to support and promote PMTCT activities.There were misunderstandings by community members on the free formula policy change. Mothers transferred the motherhood role to their mothers while partners provided inadequate financial support, leading to risky mixed feeding. Teenage mothers rarely breastfed their infants due to perceived constraints including embarrassment, sagging breasts and loss of freedom and boyfriends.At 12 weeks of age the intervention had doubled exclusive breastfeeding (EBF) (28% vs. 14%) and slightly increased infant weight and length. No difference was seen between study arms in HIV-free survival. The effect on EBF at12 weeks did not differ with maternal education or wealth levels, but was higher among HIV-negative mothers. Focusing on teenage mothers breastfeeding challenges, involvement of grandmothers and fathers in infant feeding decision-making, improving communication strategies on policy change and breastfeeding to the community and health workers and CHWs home visits supporting PMTCT activities are important for infant feeding and child health.
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| 7. |
- Karlsson, Isabella, 1980, et al.
(författare)
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Investigation of the Sunscreen Octocrylene's Interaction with Amino Acid Analogs in the Presence of UV Radiation
- 2012
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Ingår i: Photochemistry and Photobiology. - : Wiley. - 0031-8655 .- 1751-1097. ; 88:4, s. 904-912
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Tidskriftsartikel (refereegranskat)abstract
- Octocrylene is an organic UV filter, commonly used in sunscreens and cosmetics, which can give rise to both contact and photocontact allergy. Our aim was to investigate octocrylenes interaction with amino acid analogs in the presence of UV radiation to better understand the reason for octocrylenes photoallergenic capacity. The amino acid analogs were photolysed in presence and absence of octocrylene for 1 h in cyclohexane. The rate of degradation was considerably slower for all amino acid analogs when octocrylene was present in the mixture. Benzylamine, the lysine analog, did react with octocrylene during the photolysis and the corresponding amide was formed in an acylation reaction. By varying the benzylamine concentration and keeping the octocrylene concentration fixed the reaction rate was shown to be independent of the amine concentration. The same type of acylation reaction took place when octocrylene alone was photolysed in ethanol in which the ethyl ester was formed from octocrylene and ethanol. Our results suggest that octocrylenes ability to cause photocontact allergy could be due to its photoinduced reactivity toward primary amines and alcohols.
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| 8. |
- Karlsson, Isabella, 1980, et al.
(författare)
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Ketoprofen-Induced Formation of Amino Acid Photoadducts: Possible Explanation for Photocontact Allergy to Ketoprofen
- 2014
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Ingår i: Chemical Research in Toxicology. - : American Chemical Society (ACS). - 0893-228X .- 1520-5010. ; 27:7, s. 1294-1303
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Tidskriftsartikel (refereegranskat)abstract
- Photocontact allergy is a well-known side effect of topical preparations of the nonsteroidal anti-inflammatory drug ketoprofen. Photocontact allergy to ketoprofen appears to induce a large number of photocross allergies to both structurally similar and structurally unrelated compounds. Contact and photocontact allergies are explained by structural modification of skin proteins by the allergen. This complex is recognized by the immune system, which initiates an immune response. We have studied ketoprofen's interaction with amino acids to better understand ketoprofen's photoallergenic ability. Irradiation of ketoprofen and amino acid analogues resulted in four different ketoprofen photodecarboxylation products (6-9) together with a fifth photoproduct (5). Dihydroquinazoline 5 was shown to be a reaction product between the indole moiety of 3-methylindole (Trp analogue) and the primary amine benzylamine (Lys analogue). In presence of air, dihydroquinazoline 5 quickly degrades into stable quinazolinone 12. The corresponding quinazolinone (17) was formed upon irradiation of ketoprofen and the amino acids N-acetyl-L-Trp ethyl ester and L-Lys ethyl ester. The formation of these models of an immunogenic complex starts with the ketoprofen-sensitized formation of singlet oxygen, which reacts with the indole moiety of Trp. The formed intermediate subsequently reacts with the primary amino functionality of Lys, or its analogue, to form a Trp Lys adduct or a mimic thereof. The formation of a specific immunogenic complex that does not contain the allergen but that can still induce photocontact allergy would explain the large number of photocross allergies with ketoprofen. These allergens do not have to be structurally similar as long as they can generate singlet oxygen. To the best of our knowledge, there is no other suggested explanation for ketoprofen's photoallergenic properties that can account for the observed photocross allergies. The formation of a specific immunogenic complex that does not contain the allergen is a novel hypothesis in the field of contact and photocontact allergy.
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| 9. |
- Persson, Klas, 1979-, et al.
(författare)
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Diffuse hydrological mass transport through catchments : scenario analysis of coupled physical and biogeochemical uncertainty effects
- 2011
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Ingår i: Hydrology and Earth System Sciences. - : Copernicus GmbH. - 1027-5606 .- 1607-7938. ; 15:10, s. 3195-3206
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Tidskriftsartikel (refereegranskat)abstract
- This paper quantifies and maps the effects of coupled physical and biogeochemical variability on diffuse hydrological mass transport through and from catchments. It further develops a scenario analysis approach and investigates its applicability for handling uncertainties about both physical and biogeochemical variability and their different possible cross-correlation. The approach enables identification of conservative assumptions, uncertainty ranges, as well as pollutant/nutrient release locations and situations for which further investigations are most needed in order to reduce the most important uncertainty effects. The present scenario results provide different statistical and geographic distributions of advective travel times for diffuse hydrological mass transport. The geographic mapping can be used to identify potential hotspot areas with large mass loading to downstream surface and coastal waters, as well as their opposite, potential lowest-impact areas within the catchment. Results for alternative travel time distributions show that neglect or underestimation of the physical advection variability, and in particular of those transport pathways with much shorter than average advective solute travel times, can lead to substantial underestimation of pollutant and nutrient loads to downstream surface and coastal waters. This is particularly true for relatively high catchment-characteristic product of average attenuation rate and average advective travel time, for which mass delivery would be near zero under assumed transport homogeneity but can be orders of magnitude higher for variable transport conditions. A scenario of high advection variability, with a significant fraction of relatively short travel times, combined with a relevant average biogeochemical mass attenuation rate, emerges consistently from the present results as a generally reasonable, conservative assumption for estimating maximum diffuse mass loading, when the prevailing physical and biogeochemical variability and cross-correlation are uncertain.
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| 10. |
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| 11. |
- Persson, Klas, 1979-, et al.
(författare)
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Riskkvantifiering vid föroreningsspridning genom avrinningsområden
- 2010
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- För att skydda vattenresurserna inom ett avrinningsområde från förorening krävs uppskattningar både av den vattenburna föroreningsspridningen från alla befintliga föroreningskällor i området och av risken för framtida föroreningsutsläpp från nytillkomna källor (till följd av t.ex. föroreningsolyckor). I den här rapporten presenterar vi en metodik för beräkning av vattenburen föroreningsspridning från befintliga och tänkbara framtida föroreningskällor samt för uppskattning av tillhörande föroreningsrisk i termer av sannolikheten att givna gränsvärden för föroreningsnivåer överskrids i känsliga vattenmiljöer inom och nedströms ett avrinningsområde. Vi undersöker och illustrerar också metodikens användbarhet med beräkningsexempel från Forsmarks och Norrströms avrinningsområden. Den föreslagna metodiken utgörs av två beräkningssteg: I Steg 1 beräknas och karteras transporttider och transporttidsfördelningar för strömmande vatten, och vattenburna icke-reaktiva ämnen som helt följer vattnets rörelse, från olika föroreningskällor till känsliga grundvatten- och ytvattenmiljöer inom och nedströms avrinningsområdet. Resultat från detta första, ämnesoberoende steg kan användas för att identifiera de särskilt föroreningspåverkande delarna av ett avrinningsområde, varifrån utsläppta föroreningar snabbast kan spridas till en nedströms grundvatten- eller ytvattenrecipient med minst tidsutrymme för nedbrytning och andra självrenande processer längs spridningsvägarna. I Steg 2 beräknas och karteras den ämnesspecifika transporten av reaktiva föroreningar med vattnet, samt medföljande föroreningsrisker. Detta görs genom att de ämnesoberoende vattentransporttiderna och deras fördelning längs olika spridningsvägar, som beräknades i Steg 1, kopplas ihop med lämpliga modellbeskrivningar av nedbrytning och andra självreningsprocesser (som avklingning av radioaktiva ämnen och avskiljning av närsalter och metaller ur det strömmande vattnet) för olika specifika ämnen, eller grupper av ämnen med liknande processegenskaper. Våra resultat visar att det i detta beräkningssteg är viktigt att räkna med hela fördelningen av olika möjliga transporttider som kan förekomma från källa till recipient vid beräkning av vattenburen föroreningstransport. Om man bara räknar med en genomsnittlig transporttid kommer man att systematiskt underskatta den totala föroreningsmassa som når recipienten. Beräkningsosäkerheter, vad gäller karakteriseringen av föroreningskällor, vattenflöden och ämnesspridningen med vattnet, hanteras också i den föreslagna metodiken, genom sannolikhetsbaserade känslighetsanalyser. Dessa omfattar både statistisk representation av den slumpmässiga parametervariation som naturliga system ofta uppvisar samt olika antagna scenarier för nuvarande eller framtida förhållanden vars osäkerhet inte kan uppskattas i statistiska termer. På så vis kan man relativt enkelt bedöma hur stora osäkerheterna är och identifiera de intervall av spridningsförhållanden och ämnesspecifika självreningsegenskaper där osäkerheterna har stor praktisk betydelse för vattenförvaltning i ett avrinningsområde, samt de resterande, ofta bredare intervall där de inte har det. I det sistnämnda fallet får man, trots osäkerheterna, genom känslighetsanalysen en relativt säker och robust grund för beslut om exempelvis olycksberedskap och åtgärder för att begränsa föroreningsspridning från befintliga föroreningskällor. Genom att klart identifiera de fall där osäkerheterna spelar stor praktisk roll får man också ett rationellt underlag för att i dessa fall välja mellan att antingen göra fler undersökningar för att minska osäkerheterna, eller bedöma föroreningsriskerna konservativt och agera efter det sämsta av alla möjliga scenarier i vattenförvaltning, åtgärdsprogram och olycksberedskap.
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| 12. |
- Wigenius, Jens A., 1975-, et al.
(författare)
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Interactions Between a Luminescent Conjugated Oligoelectrolyte and Insulin During Early Phases of Amyloid Formation
- 2011
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Ingår i: Macromolecular Bioscience. - : Wiley. - 1616-5187 .- 1616-5195. ; 11:8, s. 1120-1127
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Tidskriftsartikel (refereegranskat)abstract
- Aggregates of misfolded proteins play an important role in diseases such as Alzheimer's. Here it is demonstrated how the anionic oligothiophene p-FTAA interacts with and influences pre-fibrillar protein assemblies during the earlier stages of in vitro fibrillation. Conjugated polythiophenes have previously been demonstrated to detect and discriminate between different types of protein aggregates and also introduce luminescent or conductive properties to these nanoscale fiber structures. Fluorescence spectroscopy, DLS, TEM and FCS are employed to follow the interplay between p-FTAA and insulin during in vitro fibrillation.
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