Artikkelit: Recent submissions

Now showing items 1-20 of 25440
  • Köster, Egle; Köster, Kajar; Berninger, Frank; Prokushkin, Anatoly; Aaltonen, Heidi; Zhou, Xuan; Pumpanen, Jukka (2018)
    Rising air temperatures and changes in precipitation patterns in boreal ecosystems are changing the fire occurrence regimes (intervals, severity, intensity, etc.). The main impacts of fires are reported to be changes in soil physical and chemical characteristics, vegetation stress, degradation of permafrost, and increased depth of the active layer. Changes in these characteristics influence the dynamics of carbon dioxide (CO2) and methane (CH4) fluxes. We have studied the changes in CO2 and CH4 fluxes from the soil in boreal forest areas in central Siberia underlain by continuous permafrost and the possible impacts of the aforementioned environmental factors on the emissions of these greenhouse gases. We have used a fire chronosequence of areas, with the last fire occurring 1, 23, 56, and more than 100 years ago. The soils in our study acted as a source of CO2. Emissions of CO2 were lowest at the most recently burned area and increased with forest age throughout the fire chronosequence. The CO2 flux was influenced by the pH of the top 5cm of the soil, the biomass of the birch (Betula) and alder (Duschekia) trees, and by the biomass of vascular plants in the ground vegetation. Soils were found to be a CH4 sink in all our study areas. The uptake of CH4 was highest in the most recently burned area (forest fire one year ago) and the lowest in the area burned 56 years ago, but the difference between fire chronosequence areas was not significant. According to the linear mixed effect model, none of the tested factors explained the CH4 flux. The results confirm that the impact of a forest fire on CO2 flux is long-lasting in Siberian boreal forests, continuing for more than 50 years, but the impact of forest fire on CH4 flux is minimal.
  • Koster, Egle; Koster, Kajar; Berninger, Frank; Aaltonen, Heidi; Zhou, Xuan; Pumpanen, Jukka (2017)
    Forest fires are one of the most important natural disturbances in boreal forests, and their occurrence and severity are expected to increase as a result of climate warming. A combination of factors induced by fire leads to a thawing of the near-surface permafrost layer in subarctic boreal forest. Earlier studies reported that an increase in the active layer thickness results in higher carbon dioxide (CO2) and methane (CH4) emissions. We studied changes in CO2, CH4 and nitrous oxide (N2O) fluxes in this study, and the significance of several environmental factors that influence the greenhouse gas (GHG) fluxes at three forest sites that last had fires in 2012, 1990 and 1969, and we compared these to a control area that had no fire for at least 100 years. The soils in our study acted as sources of CO2 and N2O and sinks for CH4. The elapsed time since the last forest fire was the only factor that significantly influenced all studied GHG fluxes. Soil temperature affected the uptake of CH4, and the N2O fluxes were significantly influenced by nitrogen and carbon content of the soil, and by the active layer depth. Results of our study confirm that the impacts of a forest fire on GHGs last for a rather long period of time in boreal forests, and are influenced by the fire induced changes in the ecosystem. (C) 2017 Elsevier B.V. All rights reserved.
  • Valiev, R. R.; Berezhnoy, A. A.; Gritsenko, I. S.; Merzlikin, B. S.; Cherepanov, Viktor N.; Kurten, Theo; Wöhler, Chrisitan (2020)
    We calculated the cross sections of photolysis of OH, LiO, NaO, KO, HCl, LiCl, NaCl, KCl, HF, LiF, NaF, and KF molecules using quantum chemistry methods. The maximal values for photolysis cross sections of alkali metal monoxides are on the order of 10^−18 cm^2. The lifetimes of photolysis for quiet Sun at 1 astronomical unit are estimated as 2.0×10^5, 28, 5, 14, 2.1×10^5, 225, 42, 52,2×10^6, 35400, 486, and 30400 s for OH, LiO, NaO, KO, HCl, LiCl, NaCl, KCl, HF, LiF, NaF, and KF, respectively. We performed a comparison between values of photolysis lifetimes obtained in this work and in previous studies. Based on such a comparison, our estimations of photolysis lifetimes of OH, HCl, and HF have an accuracy of about a factor of 2. We determined typical kinetic energies of main peaks of photolysis-generated metal atoms. Impact-produced LiO, NaO, KO, NaCl, and KCl molecules are destroyed in the lunar and Hermean exospheres almost completely during the first ballistic flight, while other considered molecules are more stable against destruction by photolysis.
  • Chaichian, M.; Mnatsakanova, M.N.; Vernov, Yu.S. (2020)
    Classical results of the axiomatic quantum field theory – irreducibility of the set of field operators, Reeh and Schlieder's theorems and generalized Haag's theorem are proven in SO(1,1) invariant quantum field theory, of which an important example is noncommutative quantum field theory. In SO(1,3) invariant theory new consequences of generalized Haag's theorem are obtained. It has been proven that the equality of four-point Wightman functions in two theories leads to the equality of elastic scattering amplitudes and thus the total cross-sections in these theories.
  • Kajava, Mika (Institutum Romanum Finlandiae, 2017)
    Acta Instituti Romani Finlandiae
  • Jalava, K.; Kauppinen, A.; Al-Hello, H.; Räsänen, S. (2019)
    A gastrointestinal outbreak was reported among 154 diners who attended a Christmas buffet on the 9 and 10 December 2016. A retrospective cohort study was undertaken. Faecal samples, water, ice and an air ventilation device were tested for indicators and routine pathogens. Altogether 26% (24/91) fulfilled the case definition of having typical viral gastrointestinal symptoms. Norovirus genogroup I was detected in faecal samples from three cases. One of these cases tested positive also for sapovirus and had a family member testing positive for both norovirus and sapovirus. A diner who drank water or drinks with ice cubes (risk ratios (RR) 6.5, 95% confidence intervals (CI) 1.5-113.0) or both (RR 8.2, 95% CI 1.7-145.5) had an increased risk in a dose-response manner. Ice cubes from three vending machines had high levels of heterotrophic bacteria. A faulty air ventilation valve in the space where the ice cube machine was located was considered a likely cause of this outbreak. Leaking air ventilation valves may represent a neglected route of transmission in viral gastrointestinal outbreaks.
  • Chen, Wei; Chen, Hao; Zheng, Dandan; Zhang, Hongbo; Deng, Lianfu; Cui, Wenguo; Zhang, Yuhui; Santos, Hélder A.; Shen, Hongxing (2020)
    Gene therapy provides an ideal potential treatment for intervertebral disk degeneration by delivering synthetic microRNAs (miRNAs) to regulate the gene expression levels. However, it is very challenging to deliver miRNAs directly, which leads to inactivation, low transfection efficiency, and short half‐life. Here, Agomir is loaded in hydrogel to construct a gene‐hydrogel microenvironment for regulating the synthesis/catabolism balance of the tissue extracellular matrix (ECM) to treat degenerative diseases. Agomir is a cholesterol‐, methylation‐, and phosphorothioate‐modified miRNA, which can mimic the function of miRNA to regulate the expression of the target gene. Agomir874 that mimics miRNA874 is synthesized to down regulate the expression of matrix metalloproteinases (MMPs) in nucleus pulposus (NP). At the same time, a polyethylene glycol (PEG) hydrogel is synthesized through Ag‐S coordination of 4‐arm PEG‐SH and silver ion solution, which has injectable, self‐healing, antimicrobial, degradable, and superabsorbent properties and matches perfectly with the mechanism of intervertebral disk. By delivering Agomir‐loaded PEG‐hydrogel to a degenerative intervertebral disk, a gene‐hydrogel microenvironment is constructed in situ, which reduces the expression of MMPs, regulates the synthesis/catabolism balance of ECM in the NP of the intervertebral disk, and improves the tissue microenvironment regeneration.
  • Wrzosek-Lipska, K.; Rezynkina, K.; Bree, N.; Zielinska, M.; Gaffney, L. P.; Petts, A.; Andreyev, A.; Bastin, B.; Bender, M.; Blazhev, A.; Bruyneel, B.; Butler, P. A.; Carpenter, M. P.; Cederkall, J.; Clement, E.; Cocolios, T. E.; Deacon, A. N.; Diriken, J.; Ekstrom, A.; Fitzpatrick, C.; Fraile, L. M.; Fransen, Ch.; Freeman, S. J.; Garcia-Ramos, J. E.; Geibel, K.; Gernhauser, R.; Grahn, T.; Guttormsen, M.; Hadinia, B.; Hadynska-Klek, K.; Hass, M.; Heenen, P. -H.; Herzberg, R. -D.; Hess, H.; Heyde, K.; Huyse, M.; Ivanov, O.; Jenkins, D. G.; Julin, R.; Kesteloot, N.; Kroell, Th.; Kruecken, R.; Larsen, A. C.; Lutter, R.; Marley, P.; Napiorkowski, P. J.; Orlandi, R.; Page, R. D.; Pakarinen, J.; Patronis, N.; Peura, P. J.; Piselli, E.; Prochniak, L.; Rahkila, P.; Rapisarda, E.; Reiter, P.; Robinson, A. P.; Scheck, M.; Siem, S.; Chakkal, K. Singh; Smith, J. F.; Srebrny, J.; Stefanescu, I.; Tveten, G. M.; Van Duppen, P.; Van de Walle, J.; Voulot, D.; Warr, N.; Wiens, A.; Wood, J. L. (2019)
    The neutron-deficient mercury isotopes serve as a classical example of shape coexistence, whereby at low energy near-degenerate nuclear states characterized by different shapes appear. The electromagnetic structure of even-mass 182-188 Hg isotopes was studied using safe-energy Coulomb excitation of neutron-deficient mercury beams delivered by the REX-ISOLDE facility at CERN. The population of 0 + 1,2, 2(1,2)(+) and 4(1)(+) states was observed in all nuclei under study. Reduced E2 matrix elements coupling populated yrast and non-yrast states were extracted, including their relative signs. These are a sensitive probe of shape coexistence and may be used to validate nuclear models. The experimental results are discussed in terms of mixing of two different configurations and are compared with three different model calculations: the Beyond Mean Field model, the Interacting Boson Model with configuration mixing and the General Bohr Hamiltonian. Partial agreement with experiment was observed, hinting to missing ingredients in the theoretical descriptions.
  • Simola, U.; Dumusque, X.; Cisewski-Kehe, J. (2019)
    Context. Stellar activity is one of the primary limitations to the detection of low-mass exoplanets using the radial-velocity (RV) technique. Stellar activity can be probed by measuring time-dependent variations in the shape of the cross-correlation function (CCF). It is therefore critical to measure with high-precision these shape variations to decorrelate the signal of an exoplanet from spurious RV signals caused by stellar activity. Aims. We propose to estimate the variations in shape of the CCF by fitting a Skew Normal (SN) density which, unlike the commonly employed Normal density, includes a Skewness parameter to capture the asymmetry of the CCF induced by stellar activity and the convective blueshift. Methods. We compared the performances of the proposed method to the commonly employed Normal density using both simulations and real observations with different levels of activity and signal-to-noise ratios. Results. When considering real observations, the correlation between the RV and the asymmetry of the CCF and between the RV and the width of the CCF are stronger when using the parameters estimated with the SN density rather than those obtained with the commonly employed Normal density. In particular, the strongest correlations have been obtained when using the mean of the SN as an estimate for the RV. This suggests that the CCF parameters estimated using a SN density are more sensitive to stellar activity, which can be helpful when estimating stellar rotational periods and when characterizing stellar activity signals. Using the proposed SN approach, the uncertainties estimated on the RV defined as the median of the SN are on average 10% smaller than the uncertainties calculated on the mean of the Normal. The uncertainties estimated on the asymmetry parameter of the SN are on average 15% smaller than the uncertainties measured on the Bisector Inverse Slope Span (BIS SPAN), which is the commonly used parameter to evaluate the asymmetry of the CCF. We also propose a new model to account for stellar activity when fitting a planetary signal to RV data. Based on simple simulations, we were able to demonstrate that this new model improves the planetary detection limits by 12% compared to the model commonly used to account for stellar activity. Conclusions. The SN density is a better model than the Normal density for characterizing the CCF since the correlations used to probe stellar activity are stronger and the uncertainties of the RV estimate and the asymmetry of the CCF are both smaller.
  • Kerst, Thomas; Toivonen, Juha (2019)
    Remote detection of alpha radiation is commonly realised by collecting the light, the radioluminescence, that is produced when alpha particles are stopped in air. Radioluminescence of nitric oxide (NO) is primarily emitted between 200 nm and 300 nm, which makes it possible to use it for remote detection under daylight conditions. Quenching by ambient oxygen and water vapour, however, makes it generally difficult to effectively create NO radioluminescence. We present the detection of intense NO radioluminescence in ambient air under standard indoor lighting conditions using a nitrogen purge. The nitrogen contained NO impurities that were intrinsic to the gas and had not explicitly been added. We study the mechanisms that govern the NO radioluminescence production and introduce a model to describe the dynamics of the process. The level of NO contained in the gas was found to determine how successful a purge can be. We conclude by discussing possible applications of the technique in nitrogen-flushed gloveboxes at nuclear facilities where NO concentration of 100 ppb-1ppm would be sufficient for efficient optical alpha radiation detection in standard lighting conditions.
  • Boguslavski, K.; Kurkela, A.; Lappi, T.; Peuron, J. (2019)
    We study the spectral properties of an overoccupied gluonic system far from equilibrium. Using classical Yang-Mills simulations and linear response theory, we determine the statistical and spectral functions. We measure dispersion relations and damping rates of transversally and longitudinally polarized excitations in the gluonic plasma, and also study further structures in the spectral function.
  • Sumanen, Hilla; Harkko, Jaakko; Piha, Kustaa; Pietiläinen, Olli; Rahkonen, Ossi; Kouvonen, Anne (2019)
    Objectives To identify groups of municipal employees between the ages of 20 and 34 years with distinct utilisation trajectories of primary care services provided by occupational health service (OHS), measured as the annual number of OHS visits, and to identify demographic and socioeconomic risk factors that distinguish employees in the high utilisation trajectory group(s). Methods The present study is a retrospective register-based cohort study. All municipal employees of the City of Helsinki, Finland, aged 20–34 in the Helsinki Health Study, recruited from 2004 to 2013, with follow-up data for 4 years were included in the study (n=9762). The outcome measure was group-based trajectories of OHS utilisation, identified with a group-based trajectory analysis. The demographic and socioeconomic variables used to predict the outcome were age, first language, educational level and occupational class. The analyses were stratified by gender. Results A large proportion of the young employees do not use OHS. Trajectory groups of ‘No visits’ (50%), ‘Low/increasing’ (18%), ‘Low/decreasing’ (22%) and ‘High/recurrent’ (10%) use were identified. We found occupational class differences in OHS utilisation patterns showing that lower occupational classes had a higher propensity for ‘High/recurrent’ OHS utilisation for both genders. Conclusions Preventive measures should be targeted particularly to the trajectory groups of ‘Low/increasing’ and ‘High/recurrent’ in order to intervene early. In addition, OHS utilisation should be closely monitored among the two lowest occupational classes. More research with longitudinal OHS data is needed.
  • Roy, J.; Tschakert, P.; Waisman, H.; Halim, S. Abdul; Antwi-Agyei, P.; Dasgupta, P.; Hayward, B.; Kanninen, M.; Liverman, D.; Okereke, C.; Pinho, P. F.; Riahi, K.; Rodriguez, A. G. Suarez (Intergovernmental Panel on Climate Change, 2018)
    This chapter takes sustainable development as the starting point and focus for analysis. It considers the broad and multifaceted bi-directional interplay between sustainable development, including its focus on eradicating poverty and reducing inequality in their multidimensional aspects, and climate actions in a 1.5°C warmer world. These fundamental connections are embedded in the Sustainable Development Goals (SDGs). The chapter also examines synergies and trade-offs of adaptation and mitigation options with sustainable development and the SDGs and offers insights into possible pathways, especially climate-resilient development pathways towards a 1.5°C warmer world.
  • Härkki, Tellervo; Seitamaa-Hakkarainen, Pirita; Hakkarainen, Kai (2018)
    While sketching has an established role in professional design, its benefits and role in design education are subjects that invite research and opinions. We investigated how undergraduates studying to become design educators and textile teachers used sketching to generate and develop design solutions in a collaborative setting. The students were given an authentic design assignment involving three detailed tasks, one of which was 2D visualisation by sketching. Adopting a micro-analytical approach, we analysed the video-recorded visualisation session to understand how teams used sketching to collaborate and to generate and develop design solutions. To that end, we set three research questions: (1) What ways of collaborative working are reflected in actions of sketching? (2) In what ways do sequences of collaborative sketching contribute to designing? (3) What kinds of collaborative sequences of sketching advance designing? Our analysis identified three collaborative ways of sketching (co-ordinated, collective and disclosed) and confirmed that sketching is an important facilitator of mutual appropriation, adaption and adoption. Next, we identified three ways of contributing to designing, as well as three functions and six capacities for advancing designing. Our analysis shows that sketching can lead to invaluable advances in designing, although each team had its own way of using and benefiting from sketching. We further consider that the teams' diverse sketching processes and rich content owed, at least in part, to the task structure and imposed constraints. We continue to see sketching as an important design tool, one among many.
  • Halla-aho, Hilla (Oxford University Press, 2018)
    Oxford Studies in Ancient Documents
  • Leppälahti, Suvi; Gissler, M.; Mentula, M.; Heikinheimo, O. (2012)
  • Lipponen, Lasse; Kumpulainen, Kristiina; Paananen, Maiju (Springer, 2018)
    Springer International Handbooks of Education
  • Lipponen, Lasse (Sage, 2017)