945 research outputs found
Processes influencing dissolved iron distributions below the surface at the Atlantic Ocean - Celtic Sea shelf edge
No full textShelf break systems are highly dynamic environments. However little is known about the influence that benthic interactions and water mass mixing may have on vertical distributions of iron in these systems. Dissolved Fe (< 0.4 ?m) concentrations were measured in samples from nine vertical profiles across the upper slope (150–2950 m water depth) at the Atlantic Ocean–Celtic Sea shelf break. Dissolved iron concentrations varied between less than 0.2 and 5.4 nM, and the resulting detailed section showed evidence of a range of processes influencing the Fe distributions. The near sea floor data were interpreted in terms of release and removal processes. The concentrations of dissolved Fe present in near seabed waters were consistent with release of Fe from in situ remineralisation of particulate organic matter at two upper slope stations, and possibly release from pore water upon resuspension on shelf. Lateral transport of dissolved iron was evident from elevated Fe concentrations in an intermediate nepheloid layer and its advection along isopycnals. Surface waters at the shelf break also showed evidence of vertical mixing of deeper iron-rich waters. These waters contained macronutrients that sustained primary productivity in these otherwise nutrient-depleted surface waters. The data also suggest some degree of stabilisation of relatively high concentrations of iron, presumably through ligand association or as colloids. This study supports the view that lateral export of dissolved iron to the interior of the ocean from shelf and coastal zones and may have important implications for the global budget of oceanic iron
Implementation of a method to determine sub-nanomolar concentrations of iron in seawater and its application to the study of marine iron biogeochemistry at the ocean-shelf interface
No full textThe aim of this study was to improve our understanding of the marine iron cycle using a newly implemented technique to measure dissolved iron in seawater. The setting up of a flow-injection analyser with chemiluminescence detection (FIACL) for Fe(II) proved to be non-trivial. Extensive work was undertaken to solve problems relating to our limited level of understanding of the CL reaction, and the variable behaviour of the resins prepared to preconcentrate iron. An analyser for Fe(II)+(III) was optimised, and careful assessment of data demonstrated the high quality of the information interpreted in this study, from the Celtic Sea shelf edge (Northeast Atlantic), and from the North Scotia Ridge (Southern Ocean).The distribution of iron at the Celtic Sea shelf edge was examined, and was used to provide a conceptual framework for future studies. Dissolved Fe (< 0.4 µm) concentrations were measured in samples from nine vertical profiles taken across the continental slope (160 – 2950 m water depth). Dissolved iron concentrations varied between 0.2 and 5.4 nM, and the resulting detailed section showed evidence of a range of processes influencing the iron distributions. The presence of elevated levels of dissolved Fe near the seafloor was consistent with release of Fe from in situ particulate organic matter remineralisation at two upper slope stations, and possibly of pore water release upon resuspension on shelf. Lateral transport of dissolved iron was evident in an intermediate nepheloid layer and its advection along an isopycnal. Surface waters at the shelf break also showed evidence of vertical mixing of deeper iron-rich waters. The data also suggest some degree of stabilisation of relatively high concentrations of iron, presumably through ligand association or as colloids. The possibility of iron limitation of phytoplankton at the shelf edge was not ruled out despite obvious depletion of nitrate. This study supports the view that export of dissolved iron laterally to the ocean’s interior from shelf and coastal zones may have important implications for the global
budget of oceanic iron.A set of surface samples collected on a survey between the Falkland Islands and South Georgia were analysed for total dissolvable iron. Results suggested a source of benthic iron near South Georgia. A shift in photo-physiology of phytoplankton towards South Georgia was probably influenced by the transition from iron-limited to iron-replete populations. These results therefore strongly support the hypothesis that South Georgia may be a "pulse-point" of iron to high-nutrient low-chlorophyll waters
Dispersive properties of high order nedelec/edge element approximation of the time-harmonic Maxwell equations
No full textThe dispersive behaviour of high-order Næ#169;dæ#169;lec element approximation of the time harmonic Maxwell equations at a prescribed temporal frequency ω on tensor-product meshes of size h is analysed. A simple argument is presented, showing that the discrete dispersion relation may be expressed in terms of that for the approximation of the scalar Helmholtz equation in one dimension. An explicit form for the one-dimensional dispersion relation is given, valid for arbitrary order of approximation. Explicit expressions for the leading term in the error in the regimes where ωh is small, showing that the dispersion relation is accurate to order 2p for a pth-order method; and in the high-wavenumber limit where 1«ωh, showing that in this case the error reduces at a super-exponential rate once the order of approximation exceeds a certain threshold, which is given explicitly
Numerical simulations for type II superconductors: Finite Element Method for the time-dependent Ginzburg-Landau equations
No full textSuperconductivity was discovered in 1911 and since then it has become indispensable in a wide range of fields. It is often accompanied by strong magnetic fields which can do away with the superconducting properties of the material. This process is described by the Ginzburg-Landau theory of superconductivity. In this report, this theory is discussed at length. The result is a system of two coupled, time-dependent partial differential equations that can be solved using numerical methods. A nite element method is constructed using standard Lagrangian and curl-conforming Nedelec elements. Numerical simulations were performed with Lagrangian and Nedelec elements in COMSOL and MATLAB respectively. Using Lagrangian elements delivers flawed results. Using Nedelec elements should improve these results but so far only parts of the problem have successfully been solved using these elements
Evaluation of hierarchical vector basis functions for quadrilateral cells
No full textNew hierarchical vector basis functions for quadrilateral cells are introduced, and the matrix condition numbers associated with their use are compared to those of existing vector basis families to assess the relative linear independence of the functions. Scale factors are employed to improve the condition numbers. In addition, the proper use of subsets of these families to transition from one order to another (as needed for adaptive -refinement) without exciting spurious modes is considere
Metabolinen terveys ja lihavuus: varhaiset tekijät, kehityskaaret ja kausaalisuhdeanalyysi Pohjois-Suomen syntymäkohorteissa 1966 ja 1986
No full textAbstractThe obesity epidemic has grown over the last four decades in most European countries including Finland where 21.5% of women and 20% of men are now living with obesity. There is a large body of evidence establishing that the first years of life, including the foetal period, are critical for obesity and general health later in life. However, a better understanding of the link between early life determinants and the life-course trajectory of obesity is needed.In this thesis, associations between early life determinants and cardio-metabolically healthy obesity, defined as obesity in the absence of any cardiometabolic disorders, were investigated. The relationships between early life determinants and developmental body mass index (BMI) trajectories were explored. Finally, the associations between temperament traits and cardiovascular health and whether eating behaviours and fitness mediated the associations were examined. The research was conducted on data from the prospective Northern Finland Birth Cohorts 1966 (NFBC1966) and 1986 (NFBC1986) using association analyses, latent trajectory modelling and causal mediation analysis.The first study suggested that early life determinants such as age at adiposity rebound were associated with cardio-metabolically healthy obesity and that the association differed between males and females. In the second study, developmental BMI trajectories were modelled from NFBC1966 and NFBC1986. Adverse maternal factors were associated with unfavourable BMI trajectories. A different pattern of association between age at adiposity peak and BMI trajectories was found between the different cohorts, uncovering secular trends. The third study provided evidence that associations between temperament traits, established early in life, and cardiovascular health measures could be sex-specific. Furthermore, eating behaviours and mediators involved in the associations seemed to be associated with sex.The research undertaken in this thesis provides evidence to support the effect of early life determinants on life-course metabolic health and highlights the role of sex in these pathways. In addition, this work further advances the importance of psychological factors in relation to metabolic health with a specific focus on sex-specific temperament and behavioural mediators.Original papersOriginal papers are not included in the electronic version of the dissertation.Nedelec, R., Jokelainen, J., Miettunen, J., Ruokonen, A., Herzig, K.-H., Männikkö, M., Järvelin, M.-R., & Sebert, S. (2018). Early determinants of metabolically healthy obesity in young adults: study of the Northern Finland Birth Cohort 1966. International Journal of Obesity, 42(10), 1704–1714. https://doi.org/10.1038/s41366-018-0115-0Self-archived versionNedelec, R., Miettunen, J., Männikkö, M., Järvelin, M.-R., & Sebert, S. (2021). Maternal and infant prediction of the child BMI trajectories; studies across two generations of Northern Finland birth cohorts. International Journal of Obesity, 45(2), 404–414. https://doi.org/10.1038/s41366-020-00695-0Self-archived versionNedelec, R., Miettunen, J., Männikkö, M., Sebert, S., & Järvelin, M.-R. (2023). Temperament and lipid metabolism, a mediation analysis – A Northern Finland Birth Cohort 1966 study. Manuscript in preparation.TiivistelmäLihavuus on yleistynyt viimeisen neljän vuosikymmenen aikana useimmissa Euroopan maissa, myös Suomessa. Suomessa naisista 21,5 % ja miehistä 20 % on ylipainoisia. Aiempien tutkimusten mukaan ensimmäiset elinvuodet, sikiökausi mukaan luettuna, ovat tärkeitä myöhemmän lihavuuden ja yleisen terveyden kannalta. Tieto elämän varhaisvaiheisiin liittyvien tekijöiden ja lihavuuden kehityksen välisestä yhteydestä on kuitenkin puutteellista.Tämän väitöskirjan ensimmäisessä osatyössä tutkittiin elämän varhaisvaiheiden tekijöiden yhteyttä kardiometabolisesti terveeseen lihavuuteen, joka määritellään lihavuudeksi ilman verenkiertoelimistön sairauksia tai niiden tunnettuja riskitekijöitä. Toisessa osatyössä tutkittiin elämän varhaisvaiheiden tekijöiden ja painoindeksin kehityskaarten välisiä suhteita. Viimeisessä osatyössä tutkittiin temperamentin ja metabolisen terveyden, veren rasva-arvojen, välisiä yhteyksiä sekä näiden yhteyksien välittymistä syömiskäyttäytymisen ja fyysisen kunnon kautta. Tutkimus tehtiin Pohjois-Suomen syntymäkohorteissa 1966 (NFBC1966) ja 1986 (NFBC1986) käyttäen assosiaatioanalyysejä, latenttikasvukäyrämallinnusta sekä kausaalisuhdeanalyysejä.Ensimmäisessä osatyössä havaittiin, että elämän varhaisvaiheiden tekijät vaikuttivat kardiometabolisesti terveeseen lihavuuteen. Tällainen tekijä oli esimerkiksi ikä, jossa leikki-ikäisen lapsen painoindeksi on pienin ennen kuin se alkaa jälleen kasvaa (engl. adiposity rebound). Vaikutus oli kuitenkin erilainen miehillä ja naisilla. Toisessa tutkimuksessa painoindeksin kehityskaaret mallinnettiin NFBC1966 ja NFBC1986 -kohorteissa. Äidin tupakointi ja raskautta edeltänyt korkeampi painoindeksi olivat yhteydessä lapsen epäsuotuisaan painoindeksin kehityskaareen. Yhteys imeväisiän painoindeksin kasvukäyrän huipun ajoittumisen ja mallinnetun painoindeksin kehityskaaren välillä oli kohorteissa erilainen, mikä viittaa aikakaudellisiin ympäristön vaikutuksiin. Kolmannessa työssä tutkittiin erilaisia temperamenttipiirteitä, jotka myös ilmenivät varhaisella iällä. Työ osoitti, että temperamentti on yhteydessä veren rasva-arvoihin, mutta osin eri tavoin eri sukupuolilla. Lisäksi havaittiin miesten ja naisten välisiä eroja siinä, miten elintavat välittivät temperamenttipiirteiden ja veren rasva-arvojen välisiä yhteyksiä.Tämän väitöskirjan tulokset tarjoavat lisänäyttöä elämän varhaisvaiheen tekijöiden yhteyksistä metaboliseen terveyteen läpi elämän ja korostavat sukupuolten välisiä eroja. Tulokset vahvistavat käsitystä metaboliseen terveyteen vaikuttavien tekijöiden monimuotoisuudesta temperamentista terveyskäyttäytymiseen läpi elämän.OsajulkaisutOsajulkaisut eivät sisälly väitöskirjan elektroniseen versioon.Nedelec, R., Jokelainen, J., Miettunen, J., Ruokonen, A., Herzig, K.-H., Männikkö, M., Järvelin, M.-R., & Sebert, S. (2018). Early determinants of metabolically healthy obesity in young adults: study of the Northern Finland Birth Cohort 1966. International Journal of Obesity, 42(10), 1704–1714. https://doi.org/10.1038/s41366-018-0115-0Rinnakkaistallennettu versioNedelec, R., Miettunen, J., Männikkö, M., Järvelin, M.-R., & Sebert, S. (2021). Maternal and infant prediction of the child BMI trajectories; studies across two generations of Northern Finland birth cohorts. International Journal of Obesity, 45(2), 404–414. https://doi.org/10.1038/s41366-020-00695-0Rinnakkaistallennettu versioNedelec, R., Miettunen, J., Männikkö, M., Sebert, S., & Järvelin, M.-R. (2023). Temperament and lipid metabolism, a mediation analysis – A Northern Finland Birth Cohort 1966 study. Manuscript in preparation.Academic dissertation to be presented with the assent of the Doctoral Programme Committee of Health and Biosciences of the University of Oulu for public defence in Auditorium H1091 in Dentopolis, on 12 June 2023, at 12 noonAbstract
The obesity epidemic has grown over the last four decades in most European countries including Finland where 21.5% of women and 20% of men are now living with obesity. There is a large body of evidence establishing that the first years of life, including the foetal period, are critical for obesity and general health later in life. However, a better understanding of the link between early life determinants and the life-course trajectory of obesity is needed.
In this thesis, associations between early life determinants and cardio-metabolically healthy obesity, defined as obesity in the absence of any cardiometabolic disorders, were investigated. The relationships between early life determinants and developmental body mass index (BMI) trajectories were explored. Finally, the associations between temperament traits and cardiovascular health and whether eating behaviours and fitness mediated the associations were examined. The research was conducted on data from the prospective Northern Finland Birth Cohorts 1966 (NFBC1966) and 1986 (NFBC1986) using association analyses, latent trajectory modelling and causal mediation analysis.
The first study suggested that early life determinants such as age at adiposity rebound were associated with cardio-metabolically healthy obesity and that the association differed between males and females. In the second study, developmental BMI trajectories were modelled from NFBC1966 and NFBC1986. Adverse maternal factors were associated with unfavourable BMI trajectories. A different pattern of association between age at adiposity peak and BMI trajectories was found between the different cohorts, uncovering secular trends. The third study provided evidence that associations between temperament traits, established early in life, and cardiovascular health measures could be sex-specific. Furthermore, eating behaviours and mediators involved in the associations seemed to be associated with sex.
The research undertaken in this thesis provides evidence to support the effect of early life determinants on life-course metabolic health and highlights the role of sex in these pathways. In addition, this work further advances the importance of psychological factors in relation to metabolic health with a specific focus on sex-specific temperament and behavioural mediators.Tiivistelmä
Lihavuus on yleistynyt viimeisen neljän vuosikymmenen aikana useimmissa Euroopan maissa, myös Suomessa. Suomessa naisista 21,5 % ja miehistä 20 % on ylipainoisia. Aiempien tutkimusten mukaan ensimmäiset elinvuodet, sikiökausi mukaan luettuna, ovat tärkeitä myöhemmän lihavuuden ja yleisen terveyden kannalta. Tieto elämän varhaisvaiheisiin liittyvien tekijöiden ja lihavuuden kehityksen välisestä yhteydestä on kuitenkin puutteellista.
Tämän väitöskirjan ensimmäisessä osatyössä tutkittiin elämän varhaisvaiheiden tekijöiden yhteyttä kardiometabolisesti terveeseen lihavuuteen, joka määritellään lihavuudeksi ilman verenkiertoelimistön sairauksia tai niiden tunnettuja riskitekijöitä. Toisessa osatyössä tutkittiin elämän varhaisvaiheiden tekijöiden ja painoindeksin kehityskaarten välisiä suhteita. Viimeisessä osatyössä tutkittiin temperamentin ja metabolisen terveyden, veren rasva-arvojen, välisiä yhteyksiä sekä näiden yhteyksien välittymistä syömiskäyttäytymisen ja fyysisen kunnon kautta. Tutkimus tehtiin Pohjois-Suomen syntymäkohorteissa 1966 (NFBC1966) ja 1986 (NFBC1986) käyttäen assosiaatioanalyysejä, latenttikasvukäyrämallinnusta sekä kausaalisuhdeanalyysejä.
Ensimmäisessä osatyössä havaittiin, että elämän varhaisvaiheiden tekijät vaikuttivat kardiometabolisesti terveeseen lihavuuteen. Tällainen tekijä oli esimerkiksi ikä, jossa leikki-ikäisen lapsen painoindeksi on pienin ennen kuin se alkaa jälleen kasvaa (engl. adiposity rebound). Vaikutus oli kuitenkin erilainen miehillä ja naisilla. Toisessa tutkimuksessa painoindeksin kehityskaaret mallinnettiin NFBC1966 ja NFBC1986 -kohorteissa. Äidin tupakointi ja raskautta edeltänyt korkeampi painoindeksi olivat yhteydessä lapsen epäsuotuisaan painoindeksin kehityskaareen. Yhteys imeväisiän painoindeksin kasvukäyrän huipun ajoittumisen ja mallinnetun painoindeksin kehityskaaren välillä oli kohorteissa erilainen, mikä viittaa aikakaudellisiin ympäristön vaikutuksiin. Kolmannessa työssä tutkittiin erilaisia temperamenttipiirteitä, jotka myös ilmenivät varhaisella iällä. Työ osoitti, että temperamentti on yhteydessä veren rasva-arvoihin, mutta osin eri tavoin eri sukupuolilla. Lisäksi havaittiin miesten ja naisten välisiä eroja siinä, miten elintavat välittivät temperamenttipiirteiden ja veren rasva-arvojen välisiä yhteyksiä.
Tämän väitöskirjan tulokset tarjoavat lisänäyttöä elämän varhaisvaiheen tekijöiden yhteyksistä metaboliseen terveyteen läpi elämän ja korostavat sukupuolten välisiä eroja. Tulokset vahvistavat käsitystä metaboliseen terveyteen vaikuttavien tekijöiden monimuotoisuudesta temperamentista terveyskäyttäytymiseen läpi elämän
Repeated exposure to noise increases tolerance in a coral reef fish
No full textThis is the author accepted manuscript. The final version is freely available from the publisher via the DOI in this record.Some anthropogenic noise is now considered pollution, with evidence building that noise from human activities such as transportation, construction and exploration can impact behaviour and physiology in a broad range of taxa. However, relatively little research has considered the effects of repeated or chronic noise; extended exposures may result in habituation or sensitisation, and thus changes in response. We conducted a field-based experiment at Moorea Island to investigate how repeated exposure to playback of motorboat noise affected a coral reef fish (Dascyllus trimaculatus). We found that juvenile D. trimaculatus increased hiding behaviour during motorboat noise after two days of repeated exposure, but no longer did so after one and two weeks of exposure. We also found that naïve individuals responded to playback of motorboat noise with elevated ventilation rates, but that this response was diminished after one and two weeks of repeated exposure. We found no strong evidence that baseline blood cortisol levels, growth or body condition were affected by three weeks of repeated motorboat-noise playback. Our study reveals the importance of considering how tolerance levels may change over time, rather than simply extrapolating from results of short-term studies, if we are to make decisions about regulation and mitigation.Open Access funded by Engineering and Physical Sciences Research Council, under a Creative Commons licenseFunding was provided to: Sophie Nedelec by a studentship from EPSRC, Subacoustech and an Eiffel grant – Egide program – from Campus France; Suzanne Mills and David Lecchini by the Agence National de Recherche, ANR-11-JSV7-012-01 Live and Let Die and Partnership University Fund of the French American Cultural Exchange (Ocean Bridges Program, http://facecouncil.org/puf/); Stephen Simpson by a NERC Fellowship (NE/J500616/2); and Andrew Radford by a Defra grant (ME5207)
Analysis of finite element approximation and iterative methods for time-dependent Maxwell problems
No full textIn this dissertation we are concerned with the analysis of the finite
element method for the time-dependent Maxwell interface problem when
Nedelec and Raviart-Thomas finite elements are employed and
preconditioning of the resulting linear system when implicit time schemes
are used.
We first investigate the finite element method proposed by Makridakis and
Monk in 1995. After studying the regularity of
the solution to time
dependent Maxwell's problem and providing approximation estimates for
the Fortin operator, we are able to give the optimal error estimate for the
semi-discrete scheme for Maxwell's equations.
Then we study preconditioners for linear systems arising in the finite
element method for time-dependent Maxwell's equations using implicit
time-stepping. Such linear systems are usually very large but sparse
and can only be solved iteratively. We consider overlapping Schwarz
methods and multigrid methods and extend some existing theoretical
convergence results. For overlapping Schwarz methods, we provide numerical
experiments to confirm the theoretical analysis
Cytosim codebase extensions for a 2D T cell model
No full textCode is used in "Kinesin-4 KIF21B limits microtubule growth to allow rapid centrosome polarization in T cells", by Peter Jan Hooikaas, Hugo G.J. Damstra, Oane J. Gros, Wilhelmina E. van Riel, Maud Martin, Yesper T.H. Smits, Jorg van Loosdregt, Lukas C. Kapitein, Florian Berger, Anna Akhmanova. The code is an extended form of Cytosim, made by François Nedelec (https://gitlab.com/f.nedelec/cytosim). Only the minor extensions outside of the base code, listed in the README.txt file, can be attributed to author O.J.Gros, other authors are taken from the registered contributors on the cytosim gitlab, as having worked on the code base that was extended
Curl-conforming hierarchical vector bases for triangles and tetrahedra
No full textA new family of hierarchical vector bases is proposed for triangles and tetrahedra. These functions span the curl-conforming reduced-gradient spaces of Nédélec. The bases are constructed from orthogonal scalar polynomials to enhance their linear independence, which is a simpler process than an orthogonalization applied to the final vector functions. Specific functions are tabulated to order 6.5. Preliminary results confirm that the new bases produce reasonably well-conditioned matrice
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