| 1. |
- Anderson, Helén, et al.
(författare)
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Skapa kundnärvaro i innovationsprocessen
- 2008
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Ingår i: Innovationsförmåga. - Malmö : Holmbergs i Malmö AB. - 9789197785204 ; , s. 40-59
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Bokkapitel (populärvet., debatt m.m.)
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| 2. |
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| 3. |
- Axelsson, Ulrik, et al.
(författare)
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Strukturerad miljödatahantering inom järn- och stålindustri. Etapp 2; Miljöinformationssystem
- 2004
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- Det analysarbete som gjorts har i denna etapp har genomförts i samarbete med samma tre typföretag - Höganäs AB, Sandvik Materials Technology samt Ovako Steel AB - som i etapp 1. De tre företagen hanterar vardera en avsevärda mängd miljödata som idag finns utspridd inom organisationerna och lagras i olika system varför sammanställningar försvåras. Det betyder att den miljödata som mäts och beräknas lagras på ett sätt som innebär en irrationell hantering av den samlade miljöinformationen. Den analys som visar att det inom järn- och stålbranschen går att beskriva verksamhetsprocesser på ett enhetligt sätt och att miljödatan som företagen mäter, beräknar och lagrar överensstämmer i mycket stor grad. Baserat på detta har en branschgemensam miljödatastruktur varit möjlig att ta fram. Denna struktur är framtagen för att kunna lagra miljödata för utsläpp till luft, utsläpp till vatten, energianvändning och avfall. Utifrån den miljödatastruktur som arbetats fram och genom diskussioner med representanter för typföretagen i projektet har en översiktlig systemskiss för ett miljöinformationssystem inom järn- och stålindustrin tagits fram. Detta miljöinformationssystem kan vara generellt inom branschen och svara upp mot gemensamma krav på hantering av miljödata.
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| 4. |
- Ballantyne, Kaye N., et al.
(författare)
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Toward Male Individualization with Rapidly Mutating Y-Chromosomal Short Tandem Repeats
- 2014
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Ingår i: Human Mutation. - : John Wiley & Sons. - 1059-7794 .- 1098-1004. ; 35:8, s. 1021-1032
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Tidskriftsartikel (refereegranskat)abstract
- Relevant for various areas of human genetics, Y-chromosomal short tandem repeats (Y-STRs) are commonly used for testing close paternal relationships among individuals and populations, and for male lineage identification. However, even the widely used 17-loci Yfiler set cannot resolve individuals and populations completely. Here, 52 centers generated quality-controlled data of 13 rapidly mutating (RM) Y-STRs in 14,644 related and unrelated males from 111 worldwide populations. Strikingly, greater than99% of the 12,272 unrelated males were completely individualized. Haplotype diversity was extremely high (global: 0.9999985, regional: 0.99836-0.9999988). Haplotype sharing between populations was almost absent except for six (0.05%) of the 12,156 haplotypes. Haplotype sharing within populations was generally rare (0.8% nonunique haplotypes), significantly lower in urban (0.9%) than rural (2.1%) and highest in endogamous groups (14.3%). Analysis of molecular variance revealed 99.98% of variation within populations, 0.018% among populations within groups, and 0.002% among groups. Of the 2,372 newly and 156 previously typed male relative pairs, 29% were differentiated including 27% of the 2,378 father-son pairs. Relative to Yfiler, haplotype diversity was increased in 86% of the populations tested and overall male relative differentiation was raised by 23.5%. Our study demonstrates the value of RMY-STRs in identifying and separating unrelated and related males and provides a reference database.
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| 5. |
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| 6. |
- Bridle, Helen, 1979, et al.
(författare)
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Automated control of local solution environments in open-volume microfluidics
- 2007
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 79:24, s. 9286-9293
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Tidskriftsartikel (refereegranskat)abstract
- We present an open-volume microfluidic system capable of on-fine modification of a patterned laminar flow by using programmable inlet valves. Each separate solution environment in the flow pattern can be independently exchanged between different preloaded input solutions where each exchange requires 20 s. The number of flow patterns that can be generated by one device is N-n, where N represents the number of valve inlets and n the number of microchannels in the microfluidic system. Furthermore, the system can be operated as a combinatorial mixer, in which mixture of the different input solutions can be obtained independently in each channel. Since the flow patterns are generated in an open volume, they are accessible to many different detection methods and types of probes, e.g., microelectrodes, cells, or cell fragments. This technology offers the possibility to adjust the flow pattern composition in response to an output from a probe. This is the first step toward creating an automated feedback device controlled by, for example, biological cells.
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| 7. |
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| 8. |
- Eeg-Olofsson, Måns, 1967, et al.
(författare)
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TTCOV19: timing of tracheotomy in SARS-CoV-2-infected patients: a multicentre, single-blinded, randomized, controlled trial
- 2022
-
Ingår i: Critical Care. - : Springer Science and Business Media LLC. - 1364-8535. ; 26:1
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Tidskriftsartikel (refereegranskat)abstract
- Background: Critically ill COVID-19 patients may develop acute respiratory distress syndrome and the need for respiratory support, including mechanical ventilation in the intensive care unit. Previous observational studies have suggested early tracheotomy to be advantageous. The aim of this parallel, multicentre, single-blinded, randomized controlled trial was to evaluate the optimal timing of tracheotomy. Methods: SARS-CoV-2-infected patients within the Region Vastra Gotaland of Sweden who needed intubation and mechanical respiratory support were included and randomly assigned to early tracheotomy (<= 7 days after intubation) or late tracheotomy (>= 10 days after intubation). The primary objective was to compare the total number of mechanical ventilation days between the groups. Results: One hundred fifty patients (mean age 65 years, 79% males) were included. Seventy-two patients were assigned to early tracheotomy, and 78 were assigned to late tracheotomy. One hundred two patients (68%) underwent tracheotomy of whom sixty-one underwent tracheotomy according to the protocol. The overall median number of days in mechanical ventilation was 18 (IQR 9; 28), but no significant difference was found between the two treatment regimens in the intention-to-treat analysis (between-group difference:- 1.5 days (95% CI -5.7 to 2.8); p= 0.5). A significantly reduced number of mechanical ventilation days was found in the early tracheotomy group during the per-protocol analysis (between-group difference: - 8.0 days (95% CI - 13.8 to - 2.27); p= 0.0064). The overall correlation between the timing of tracheotomy and days of mechanical ventilation was significant (Spearman's correlation: 0.39, p < 0.0001). The total death rate during intensive care was 32.7%, but no significant differences were found between the groups regarding survival, complications or adverse events. Conclusions: The potential superiority of early tracheotomy when compared to late tracheotomy in critically ill patients with COVID-19 was not confirmed by the present randomized controlled trial but is a strategy that should be considered in selected cases where the need for MV for more than 14 days cannot be ruled out.
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| 9. |
- Granholm, Ann-Helen, et al.
(författare)
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Estimating vertical canopy cover using dense image-based point cloud data in four vegetation types in southern Sweden
- 2017
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Ingår i: International Journal of Remote Sensing. - : Informa UK Limited. - 0143-1161 .- 1366-5901. ; 38, s. 1820-1838
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Tidskriftsartikel (refereegranskat)abstract
- This study had the aim of investigating the utility of image-based point cloud data for estimation of vertical canopy cover (VCC). An accurate measure of VCC based on photogrammetric matching of aerial images would aid in vegetation mapping, especially in areas where aerial imagery is acquired regularly. The test area is located in southern Sweden and was divided into four vegetation types with sparse to dense tree cover: unmanaged coniferous forest; pasture areas with deciduous tree cover; wetland; and managed coniferous forest. Aerial imagery with a ground sample distance of 0.24 m was photogrammetrically matched to produce dense image-based point cloud data. Two different image matching software solutions were used and compared: MATCH-T DSM by Trimble and SURE by nFrames. The image-based point clouds were normalized using a digital terrain model derived from airborne laser scanner (ALS) data. The canopy cover metric vegetation ratio was derived from the image-based point clouds, as well as from raster-based canopy height models (CHMs) derived from the point clouds. Regression analysis was applied with vegetation ratio derived from near nadir ALS data as the dependent variable and metrics derived from image-based point cloud data as the independent variables. Among the different vegetation types, vegetation ratio derived from the image-based point cloud data generated by using MATCH-T resulted in relative root mean square errors (rRMSE) of VCC ranging from 6.1% to 29.3%. Vegetation ratio based on point clouds from SURE resulted in rRMSEs ranging from 7.3% to 37.9%. Use of the vegetation ratio based on CHMs generated from the image-based point clouds resulted in similar, yet slightly higher values of rRMSE.
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| 10. |
- Granholm, Ann-Helen, et al.
(författare)
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Estimating vertical canopy cover with dense point cloud data from matching of digital aerial photos
- 2015
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- This study aims to explore the use of dense point clouds from matching of aerial photos for estimation of vertical canopy cover (VCC), defined as the proportion of the forest floor covered by the vertical projection of the tree crowns. VCC is commonly estimated using vegetation ratio (VR) derived from airborne laser scanner (ALS) data. A reliable measure of VCC from matching aerial photos would aid in vegetation mapping and reduce the need for repeated ALS data acquisition. The test area is located in southern Sweden and covers a variety of vegetation types. In total 367 sample plots were placed in parts of the study area representing VCC ranging from 0 % up to close to 100 %. ALS data with a density of 20 returns per m2 was used for calculating the VR as the proportion of first returns above a threshold. Aerial imagery with a ground sample distance of 0.25 m was matched to produce dense point cloud data, which was used to derive digital surface models (DSMs) with grid size from 0.25 m up to 2.0 m. Local maxima (LM) detection was applied to the DSMs with search windows of 0.5 m size up to 2.0 m. The heights of the LM were normalized using a digital elevation model (DEM) derived from ALS data. Regression analysis was applied with the VR as dependent variable and the sum of the height of LM within sample plots as independent variable. Results from linear regression using heights of LM detected in a DSM of 0.25 m resolution with a 0.5 m search window gave an root mean square error (RMSE) of 5.5 % and relative RMSE (rRMSE) of 9.3 % in forest on rocky outcrops and boulders, while wooded pasture gave RMSE = 6.3 % and rRMSE = 19 %.
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| 11. |
- Jansens, Rianne, et al.
(författare)
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The Representation of Children’s Participation in Guidelines for Planning and Designing Public Playspaces: A Scoping Review with “Best Fit” Framework Synthesis
- 2023
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI. - 1661-7827 .- 1660-4601. ; 20:10
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Forskningsöversikt (refereegranskat)abstract
- For children, meaningful participation in community life includes being able to access places for play. Such community playspaces are potentially important for all children, including those with disabilities. Yet, children are rarely asked for their views on the design of playspaces, which can further contribute to exclusionary practices and undermine children’s rights to share their views on matters that affect them. In this scoping review, we aim to analyze guidelines and identify strategies for supporting children’s participation rights when planning public playspaces. Guidelines are practical tools used by local policymakers when creating community playspaces, which are important sites for children’s outdoor play. In total, forty-two guidelines were identified that addressed children’s participation rights, along with community involvement. Qualitative evidence synthesis with a “best fit” framework approach was used, informed by Lundy’s model of children’s participation. The findings revealed the importance of initial community involvement as a critical prerequisite. Strategies for children’s participation mostly concerned “space and voice” (for children of diverse abilities), with little attention paid to giving their views due weight. This evidence shows that there is a significant gap in knowledge surrounding policy development and implementation to support adults and children to cooperate equally in designing playspaces. Future directions for research in children’s participation require a focus on combined community–children participation approaches in public playspace design. Such work could strengthen and facilitate the role of adults as bearers of the duty to implement the rights of children. This review generated inclusive strategies in planning public playspaces, which could support local policymakers in this complex multi-layered process.
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| 12. |
- Lundmark, Annika, 1972-
(författare)
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Monitoring transport and fate of de-icing salt in the roadside environment : Modelling and field measurements
- 2008
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Roads and traffic are a major non-point source of pollutants and may have severe impacts on surface water, groundwater, soil and vegetation. In cold climates, de-icing salt is one such pollutant that may cause increased chloride concentrations and induce other effects on the environment. Monitoring and quantifying environmental effects are crucial for governing decisions towards more suitable use of de-icing salt in order to achieve and maintain good environmental status around roads. This thesis presents an operational modelling tool for monitoring the transport and fate of de-icing salt in the roadside environment in order to quantify changes in the environment at various spatial and temporal scales, using salt application data, meteorological data, geology and generic descriptions of hydrogeological environments as main inputs. A combination of modelling and various independent field measurements provided an efficient means for evaluating and describing the spread of de-icing salt from the road to the surroundings, the deposition of salt and ploughed snow in the roadside, and the corresponding increase in chloride concentration in soil and groundwater. Both the spatial and seasonal variation in soil chloride concentration were significantly affected by de-icing salt application. The importance of type of soil, vegetation type, groundwater conditions and distance from the road was clearly demonstrated for modelling the transport and fate of de-icing salt in the roadside environment. Salt emissions from the road by surface runoff were estimated at 50-80% of applied salt and transport by snow ploughing and air emissions at 20-50%. The uncertainty in the spatial distribution of snow and salt deposition close to the road was high and a previous proposed exponential decline in salt deposition with distance from the road could not be justified within a couple of metres from the road. Future monitoring should include both modelling and systematic data collection in order to reduce the uncertainty in predictions of the environmental impact of de-icing salt. Modelling of chloride concentration, soil water content and soil temperature and measurements of electrical resistivity may be a cost-effective solution for quantifying changes in the roadside environment.
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| 13. |
- Nosratabadi, Ali Reza, et al.
(författare)
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Airway contraction and cytokine release in isolated rat lungs induced by wear particles from the road and tire interface and road vehicle brakes
- 2023
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Ingår i: Inhalation Toxicology. - : Taylor & Francis. - 0895-8378 .- 1091-7691. ; 35:13-14, s. 309-323
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Tidskriftsartikel (refereegranskat)abstract
- The dominant road traffic particle sources are wear particles from the road and tire interface, and from vehicle brake pads. The aim of this work was to investigate the effect of road and brake wear particles on pulmonary function and biomarkers in isolated perfused rat lungs. Particles were sampled from the studded tire wear of three road pavements containing different rock materials in a road simulator; and from the wear of two brake pad materials using a pin-on-disk machine. Isolated rat lungs inhaled the coarse and fine fractions of the sampled particles resulting in an estimated total particle lung dose of 50 μg. The tidal volume (TV) was measured during the particle exposure and the following 50 min. Perfusate and BALF were analyzed for the cytokines TNF, CXCL1 and CCL3. The TV of lungs exposed to rock materials was significantly reduced after 25 min of exposure compared to the controls, for quartzite already after 4 min. The particles of the heavy-duty brake pads had no effect on the TV. Brake particles resulted in a significant elevation of CXCL1 in the perfusate. Brake particles showed significant elevations of all three measured cytokines, and quartzite showed a significant elevation of TNF in BALF. The study shows that the toxic effect on lungs exposed to airborne particles can be investigated using measurements of tidal volume. Furthermore, the study shows that the choice of rock material in road pavements has the potential to affect the toxicity of road wear PM10.
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| 14. |
- Olofsson, Helen, et al.
(författare)
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Aggregation effects on anhydrobiotic survival in the tardigrade Richtersius coronifer
- 2004
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Ingår i: Journal of Experimental Zoology. - : Wiley. - 0022-104X. ; 301A:2, s. 195-199
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Tidskriftsartikel (refereegranskat)abstract
- For anhydrobiotic metazoans the rate of desiccation is an important factor influencing the probability of survival in a dry anhydrobiotic state. Formation of animal aggregations, in which the exposed body surface area of individual animals is reduced, represents one way to reduce the rate of evaporation. Such aggregations have earlier been documented in e.g., nematodes. We experimentally evaluate the effect of aggregation size (number of animals in a group of desiccating animals) on anhydrobiotic survival in the eutardigrade Richtersius coronifer. The experiment shows that aggregation provides a clear improvement on anhydrobiotic survival. The most likely explanation for this is that aggregated animals were exposed to a lower rate of desiccation. Although the empirical evidence of aggregation in tardigrades is scarce, our study suggests that aggregation could potentially be an important survival factor for tardigrades living in environments characterized by periods of rapid desiccation. (C) 2004 Wiley-Liss, Inc.
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| 15. |
- Olofsson, Helen, et al.
(författare)
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Bet-hedging as an evolutionary game: the trade-off between egg size and number.
- 2009
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Ingår i: Royal Society of London. Proceedings B. Biological Sciences. - : The Royal Society. - 1471-2954. ; 276, s. 2963-2969
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Tidskriftsartikel (refereegranskat)abstract
- Bet-hedging theory addresses how individuals should optimize fitness in varying and unpredictable environments by sacrificing mean fitness to decrease variation in fitness. So far, three main bet-hedging strategies have been described: conservative bet-hedging (play it safe), diversified bet-hedging (don't put all eggs in one basket) and adaptive coin flipping (choose a strategy at random from a fixed distribution). Within this context, we analyse the trade-off between many small eggs (or seeds) and few large, given an unpredictable environment. Our model is an extension of previous models and allows for any combination of the bet-hedging strategies mentioned above. In our individual-based model (accounting for both ecological and evolutionary forces), the optimal bet-hedging strategy is a combination of conservative and diversified bet-hedging and adaptive coin flipping, which means a variation in egg size both within clutches and between years. Hence, we show how phenotypic variation within a population, often assumed to be due to non-adaptive variation, instead can be the result of females having this mixed strategy. Our results provide a new perspective on bet-hedging and stress the importance of extreme events in life history evolution.
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| 16. |
- Olofsson, Helen, et al.
(författare)
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Evolution of multi-stage dormancy in temporally autocorrelated environments.
- 2005
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Ingår i: Evolutionary Ecology Research. - 1522-0613. ; 7:8, s. 1125-1137
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Tidskriftsartikel (refereegranskat)abstract
- Question: Under what circumstances does a capacity for multi-stage dormancy (i.e. dormancy in more than one life-stage) evolve? Mathematical methods: Optimization in stochastic environments. Results are derived both analytically and by simulations. Key assumption: There exists some trade-off between resources allocated to reproduction and adult dormant survival. Different shapes of this trade-off are investigated. Major conclusions: Multi-stage dormancy can evolve in an environment with low serial autocorrelation. However, a slowly changing environment, with high positive autocorrelation, will prevent the evolution of dormancy in several life-stages. In general, a high positive environmental autocorrelation will separate the evolution of life parameters associated with active life from that of parameters associated with dormant life.
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| 17. |
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| 18. |
- Olofsson, Helén, 1965-
(författare)
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Skriftbruk i fordonsverkstaden : En studie av läs- och skrivstrategier i mötet med arbetslivets texter
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The aim of the study was to describe the reading and writing activities that takes place in vehicle repair workshops and to elucidate how people experiencing low reading-and-writing ability describe their encounters with text in working life. Reading and writing are considered in the study from an educational-philosophical and special educational perspective. This study of literacy was inspired by ethnographic methods. The empirical material consists of field notes from ten participatory observations in vehicle repair workshops, photographs from the workshops and three interviews. To see patterns in how literacy was used, literacy events were taken as the unit of analysis. The literacy environment, community of practice, reading path and technical surroundings are analytical concepts in the thematic presentation of results. Central literacy practices were characterized primarily by reading, often via computer, for information needed for solving problems. The type of reading was often non-linear, given the multimodal texts and choices in computer environments. In addition, semiotic systems and several languages were interpreted. It is important to understand how information is organised and how to handle the technology. Technology provides support structures e.g. pictorial support and translation programmes. Writing out words, button-pushing and keyboard entry to register and search for information through the use of measurement instruments and in computer-generated text environments, were central. Literacy events were embedded in the work tasks and in ongoing learning, and many literacy practices included items of both reading and writing. Social skills, plus recognizing one’s problems and asking for help, were useful strategies for handling the demands of reading and writing in working life, as were allowing time and creating concentration for the task. Interpreting pictorial matter, using technology, copying text and noting down things to remember were further strategies. Implications of the study are that effective strategies for managing the demands of reading and writing that are required in the working place should begin in school. Significant is the teachers’ approach to handling the students’ frustration when studies are not working out as expected. Caring teachers, positive energy and not giving up make a difference. General education teachers need special educational resources in the upper-secondary school in order to counteract school failure and to enhance students’ learning.
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| 19. |
- Olofsson, Helen
(författare)
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Strategy games; on survival and reproduction
- 2005
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Classical evolutionary life history concerns questions such as optimal timing of maturation, life span and number of offspring. These questions have mostly been studied theoretically under the assumption that the environment is stable and without taking into account frequency and density dependence. Life history theory is the basis for my thesis, in which I have studied the evolution of different life history strategies with a game theoretical approach incorporating both stochasticity and frequency and density dependence. The evolution of sexual reproduction has been considered enigmatic, but by incorporating competition, mating system and survival I show that sexual reproduction does not necessarily suffer from a twofold cost in terms of net population growth rate. This makes it easier to explain why sexual reproduction is such a successful and widespread reproductive strategy. I have also studied bet-hedging, i.e., risk-spreading. In a stochastic environment, where it is impossible to predict how large eggs or seeds need to be in order to survive and reproduce optimally, a female has to hedge her bets in order to make sure that some of her offspring survive. My result shows that the optimal strategy is to have variation in offspring size both within and between clutches. For some organisms, stochastic changes in weather can mean that the environment changes from livable to impossible to sustain an active life. Depending on the autocorrelation in the environment, I show that dormancy can evolve in both juveniles and adults or in just one of the stages. Changes in the environment does not necessarily have to be so detrimental that the bad periods can not sustain life. Individuals then have the two options to survive, they can either migrate or stay and adjust to the ''bad'' season. The choice that individuals make is frequency and density dependent were each individual migrates with a certain probability. Depending on parameter values, the evolutionary stable strategy ranges from obligate residency to obligate migration. When separating juvenile and adult migration probabilities, an optimal strategy is for juveniles to migrate and adults to stay as residents (depending on parameter values). This way of modeling evolutionary and ecological problems are found in frameworks such as adaptive dynamics and evolutionary game theory. The combination of evolution and ecology that adaptive dynamics uses appears to be a useful tool that can be used to solve many evolutionary questions.
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| 20. |
- Olofsson, Helen, et al.
(författare)
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The twofold cost of sex unfolded
- 2007
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Ingår i: Evolutionary Ecology Research. - 1522-0613. ; 9:7, s. 1119-1129
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Tidskriftsartikel (refereegranskat)abstract
- Question: Considering ecological factors and life history, how easy is it for sexual reproduction (as a strategy) to invade and persist in a population where all individuals are reproducing asexually? Mathematical method: We use a population growth equation that despite its simplicity captures several relevant ecological parameters: age-specific survival, differential birth rates, as well as both within-strategy and between-strategy competition. We perform invasion analysis to reach conclusions about the stability of the two evolutionary strategies. Key assumptions: Sexual and asexual reproduction can be thought of as a strategy game. Instead of focusing on the genetic advantages of sexual reproduction, we explore the ecological and demographic conditions under which the two main reproductive strategies are maintained. Conclusions: From an ecological point of view, sexual reproduction remains enigmatic only if the sexual strategy implies monogamy, there are no ecological interactions between the alternative reproductive strategies, and the life histories of both asexual and sexual strategies are limited to semelparity. Relaxation of those very restrictive ecological conditions allows for the co-existence of sexual and asexual reproduction as well as mutual invasion of the two strategies.
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| 21. |
- Olofsson, Jessica, 1975, et al.
(författare)
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A chemical waveform synthesizer
- 2005
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Ingår i: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA. - : Proceedings of the National Academy of Sciences. - 0027-8424 .- 1091-6490. ; 102:23, s. 8097-8102
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Tidskriftsartikel (refereegranskat)abstract
- Algorithms and methods were developed to synthesize complex chemical waveforms in open volumes by using a scanning-probe microfluidic platform. Time-dependent variations and oscillations of one or several chemical species around the scanning probe, such as formation of sine waves, damped oscillations, and generation of more complex patterns, are demonstrated. Furthermore, we show that intricate bursting and chaotic calcium oscillations found in biological microdomains can be reproduced and that a biological cell can be used as a probe to study receptor functionalities as a function of exposure to time-dependent variations of receptor activators and inhibitors. Thus, the method allows for studies of biologically important oscillatory reactions. More generally, the system allows for detailed studies of complex time-varying chemical and physical phenomena in solution or at solution/surface interfaces.
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| 22. |
- Olofsson, Jessica, 1975, et al.
(författare)
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Direct Access and Control of the Intracellular Solution Environment in Single Cells
- 2009
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 81:5, s. 1810-1818
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Tidskriftsartikel (refereegranskat)abstract
- Methods that can control and vary the solution environment around single cells are abundant. In contrast, methods that offer direct access to the intracellular proteome and genome in single cells with the control, flexibility, and convenience given by microfluidic methods are both scarce and in great demand. Here, we present such a method based on using a microfluidic device mounted on a programmable scanning stage and cells on-chip permeabilized by the pore-forming glycoside digitonin. We characterized the on-chip digitonin poration, as well as the solution exchange within cells. Intracellular solution exchange times vary with the dose of exposure to digitonin from less than a second to tens of seconds. Also, the degree of permeabilization obtained for cells treated with the same dose varies considerably, especially for low doses of digitonin exposure and low permeabilities. With the use of the presented setup, the degree of permeabilization can be measured during the permeabilization process, which allows for "on-line" optimization of the digitonin exposure time. Using this calibrated permeabilization method, we demonstrate the generation of intracellular oscillations, intracellular gradients, and the delivery of substrate to initiate enzymatic reactions in situ. This method holds the potential to screen and titrate intracellular receptors or enzymes or to generate intracellular oscillations, useful in the study of signaling pathways and oscillation decoding among other applications.
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| 23. |
- Olofsson, Jessica, 1975, et al.
(författare)
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Probing enzymatic activity inside single cells.
- 2013
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Ingår i: Analytical Chemistry. - : American Chemical Society (ACS). - 0003-2700 .- 1520-6882. ; 85:21, s. 10126-33
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Tidskriftsartikel (refereegranskat)abstract
- We report a novel approach for determining the enzymatic activity within a single suspended cell. Using a steady-state microfluidic delivery device and timed exposure to the pore-forming agent digitonin, we controlled the plasma membrane permeation of individual NG108-15 cells. Mildly permeabilized cells (∼100 pores) were exposed to a series of concentrations of fluorescein diphosphate (FDP), a fluorogenic alkaline phosphatase substrate, with and without levamisole, an alkaline phosphatase inhibitor. We generated quantitative estimates for intracellular enzyme activity and were able to construct both dose-response and dose-inhibition curves at the single-cell level, resulting in an apparent Michaelis contant Km of 15.3 μM ± 1.02 (mean ± standard error of the mean (SEM), n = 16) and an inhibition constant Ki of 0.59 mM ± 0.07 (mean ± SEM, n = 14). Enzymatic activity could be monitored just 40 s after permeabilization, and five point dose-inhibition curves could be obtained within 150 s. This rapid approach offers a new methodology for characterizing enzyme activity within single cells.
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| 24. |
- Rasul, Hedi
(författare)
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Water in roads: Flow paths and pollutant spread
- 2018
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- For better road construction and maintenance while minimising damage to the environment and groundwater, it is essential to monitor and model hydrological impacts on roads and consider pollution of groundwater. Water content in unbound material in road layers changes continuously and water flow usually occurs along pathways that are the main corridors for pollutant spread to groundwater. Good awareness of hydrological conditions and of water and solute transport in road layers down to the groundwater can be helpful in minimising environmental impacts during construction and operation. Today, road planning is usually carried out without specifically considering hydrological criteria. To improve understanding of the links between water in roads and groundwater, this thesis developed investigation methods and used numerical simulations for estimating seasonal variations, flow pathways and pollutant spread.Seasonal changes in road water content in an operational road, tracer tests pathways from the road shoulder and percolation down to groundwater were monitored non-destructively using electrical resistivity tomography (ERT). Chloride concentration changes were estimated based on ERT data inversion. New monitoring methodology was assessed and data analysis was performed on ERT data from different road zones and layers, which were analysed statistically and correlated to precipitation, temperature and ground moisture content. Data were collected at a unique road test station on a motorway north-west of Stockholm and in tracer experiments on typical roads in southern and central Sweden. Two-dimensional (2D) models of heat and moisture changes were prepared for a road section, considering vapour pressure and frozen water content changes using partial differential equations (PDE). Model parameters were optimised based on soil moisture and temperature data from the E18 road test station. A PDE model was used for calculating liquid water and ice content changes in different scenarios based on geometry and design changes. Both pathways and travel times were traced by 2D and pseudo 3D inverse modelling of the ERT measurements.The field data revealed clear preferential pathways of moisture and salt in the road shoulders that varied significantly during different seasons. Most infiltration occurred directly into the road shoulder, but entered the road embankment with higher percolation speed in modern roads than in old roads consisting of natural soils. The simulations showed that seasonal climate changes and the upper boundary condition were key factors determining water content in different road layers. These findings advance understanding of water in roads and represent a step towards more sustainable and environmental friendly road construction and maintenance. In addition the research results give lessons for practice both regarding monitoring and road construction. For monitoring it provides a new method in data collection and analysis. For construction and maintenance, mitigation measures are suggested, which comprise a tight road shoulder, by e.g. adding a fine grained layer on the shoulder or covering with vegetation.
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| 25. |
- Ripa, Jörgen, et al.
(författare)
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What is bet-hedging, really?
- 2009
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Ingår i: Proceedings of the Royal Society B: Biological Sciences. - : The Royal Society. - 1471-2954 .- 0962-8452. ; 277:1685, s. 1153-1154
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Tidskriftsartikel (refereegranskat)abstract
- Bet-hedging is defined as a strategy that reduces the temporal variance in fitness at the expense of a lowered arithmetic mean fitness. After a few technical points, we will here argue that this definition of bet-hedging is badly suited for models with density- and/or frequency-dependent fitness. A strict interpretation cannot be employed; possibly, a modified definition is necessary.
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