# University of Tartu

• Tartu, Estonia
Recent publications
Smartphones allow for several daily life enhancements and productivity improvements. Yet, over the last decade the concern regarding daily life adversities in relation to excessive smartphone use have been raised. This type of behavior has been regarded as “problematic smartphone use” (PSU) to describe the effects resembling a behavioral addiction. In addition to other problems in daily life, research has consistently shown that PSU is linked to various psychopathology constructs. The aim of this chapter is to provide an overview of some findings in PSU research regarding associations with psychopathology. We also discuss some of the theoretical explanations that may be helpful in conceptualizing PSU. We then take a look at self-reported PSU in relation to objectively measured smartphone use, and, finally, provide some insight into current findings and future opportunities in objectively measuring smartphone use in association with psychopathology measures. This chapter may be useful as an introductory overview into the field of PSU research.
Background: There has been a growing interest in the role of vitamin D for the well-being and physical performance of humans under heavy training such as conscripts in military service; however, there is a lack of long-term supplementation studies performed on members of this type of young, physically active, male population. The hypothesis of the study was that vitamin D supplementation during wintertime will decrease the prevalence of critically low vitamin D blood serum levels and increase hand grip strength during the winter season among young male conscripts. Study design: Longitudinal, triple-blinded, randomized, placebo-controlled trial. Methods: Fifty-three male conscripts from the Estonian Army were randomized into two groups: 27 to an intervention group and 26 to a placebo group. The groups were comparable in terms of their demographics. The intervention group received 1200 IU (30 µg) capsules of vitamin D3, and the control group received placebo oil capsules once per day. The length of the follow-up was 7 months, from October 2016 until April 2017. Blood serum vitamin D (25(OH)D), parathyroid hormone (PTH), calcium (Ca), ionized calcium (Ca-i), testosterone and cortisol values, and hand grip strength were measured four times during the study period. Results: The mean 25(OH)D level decreased significantly in the control group to a critically low level during the study, with the lowest mean value of 22 nmol/l found in March 2017. At that time point, 65% in the control group vs 15% in the intervention group had 25(OH)D values of less than 25 nmol/l (p < 0.001). In the intervention group, the levels of 25(OH)D did not change significantly during the study period. All other blood tests revealed no significant differences at any time point. The corresponding result was found for hand grip strength at all time points. Conclusion: Long-term vitamin D supplementation during wintertime results in fewer conscripts in the Estonian Army with critically low serum vitamin D (25(OH)D) levels during the winter season. However, this did not influence their physical performance in the form of the hand grip strength test.
The majority of risk loci identified by genome-wide association studies (GWAS) are in non-coding regions, hampering their functional interpretation. Instead, transcriptome-wide association studies (TWAS) identify gene-trait associations, which can be used to prioritize candidate genes in disease-relevant tissue(s). Here, we aimed to systematically identify susceptibility genes for coronary artery disease (CAD) by TWAS. We trained prediction models of nine CAD-relevant tissues using EpiXcan based on two genetics-of-gene-expression panels, the Stockholm-Tartu Atherosclerosis Reverse Network Engineering Task (STARNET) and the Genotype-Tissue Expression (GTEx). Based on these prediction models, we imputed gene expression of respective tissues from individual-level genotype data on 37,997 CAD cases and 42,854 controls for the subsequent gene-trait association analysis. Transcriptome-wide significant association (i.e. P < 3.85e−6) was observed for 114 genes. Of these, 96 resided within previously identified GWAS risk loci and 18 were novel. Stepwise analyses were performed to study their plausibility, biological function, and pathogenicity in CAD, including analyses for colocalization, damaging mutations, pathway enrichment, phenome-wide associations with human data and expression-traits correlations using mouse data. Finally, CRISPR/Cas9-based gene knockdown of two newly identified TWAS genes, RGS19 and KPTN , in a human hepatocyte cell line resulted in reduced secretion of APOB100 and lipids in the cell culture medium. Our CAD TWAS work (i) prioritized candidate causal genes at known GWAS loci, (ii) identified 18 novel genes to be associated with CAD, and iii) suggested potential tissues and pathways of action for these TWAS CAD genes.
Lobbying activity is subject to strict disclosure requirements in the USA. Failure to comply with these requirements can lead to criminal and civil penalties. It is claimed that these tight lobbying disclosure measures resulted in an increase in ‘underground lobbying’. This research proposes a method to discover non-compliance in lobbying disclosure and gauge the magnitude of underground lobbying. We start from the premise that lobbying changes the text of the bills it targets. If these changes happen to some extent systematically, then the texts of lobbied bills should be discernible from non-lobbied bills. We combine the corpus of US legislative bills with a large dataset of lobbying activity to give us a partially labelled dataset, where a positive label indicates a lobbied bill, and the lack of a label indicates either that the bill was lobbied, or was lobbied but not disclosed. To address this partial labelling problem, we first set up a naive classification task, where we assume all unlabelled bills to have a negative label and train a model on a large corpus of US bills. By finding the best performing model, we then design a bagging method and collect out of fold predictions, to predict for each unlabelled bill whether it was lobbied or not. From these predictions, we infer that there are a sizable number of bills that are likely to have been lobbied, but this lobbying activity was not disclosed. We then investigate how the political affiliation of the sponsoring senators and congressmen relates to these probabilities.
Cellulases are a group of enzymes, which catalyse different steps of cellulose hydrolysis, and are broadly used in industry as unpurified mixtures of several enzymes. The total activity of cellulase is defined as the ability of the enzyme to produce glucose, which is the final product of cellulose hydrolysis, and is expressed in cellulase units. However, common strategies for the determination of the cellulolytic activity of industrial cellulase preparations are based on the assessment of different steps of cellulose hydrolysis, and the results obtained with different methods are not similar. The aim of the present study was to develop an assay for the determination of cellulase activity that relies on the amperometric determination of the final product of cellulose hydrolysis glucose. The assay conditions were optimized using response surface methodology (RSM) combined with Box-Behnken design. The detection limit of the proposed method was 1.71 ± 0.06 U. We compared the results of the amperometric method with the ones obtained with the spectrophotometric method and viscosimetry in a commercial cellulose preparation.
Background Several reports have provided crucial evidence in animal models that epigenetic modifications, such as DNA methylation, may be involved in psychostimulant-induced stable changes at the cellular level in the brain. Epigenetic editors DNA methyltransferases (DNMTs) and ten-eleven translocation enzymes (TETs) coordinate expression of gene networks, which then manifest as long-term behavioural changes. However, the extent to which aberrant DNA methylation is involved in the mechanisms of substance use disorder in humans is unclear. We previously demonstrated that cocaine modifies gene transcription, via DNA methylation, throughout the brain and in peripheral blood cells in mice. Results We treated human peripheral blood mononuclear cells (PBMCs) from healthy male donors ( n = 18) in vitro with psychostimulants (amphetamine, cocaine). After treatment, we assessed mRNA levels and enzymatic activities of TETs and DNMTs, conducted genome-wide DNA methylation assays and next-generation sequencing. We found that repeated exposure to psychostimulants decreased mRNA levels and enzymatic activity of TETs and 5-hydroxymethylation levels in PBMCs. These data were in line with observed hyper- and hypomethylation and mRNA expression of marker genes ( IL-10, ATP2B4 ). Additionally, we evaluated whether the effects of cocaine on epigenetic editors (DNMTs and TETs) and cytokines interleukin-6 (IL-6) and IL-10 could be reversed by the DNMT inhibitor decitabine. Indeed, decitabine eliminated cocaine’s effect on the activity of TETs and DNMTs and decreased cytokine levels, whereas cocaine increased IL-6 and decreased IL-10. Conclusions Our data suggest that repeated psychostimulant exposure decreases TETs’ enzymatic activity in PBMCs. Co-treatment with decitabine reversed TETs’ levels and modulated immune response after repeated cocaine exposure. Further investigation is needed to clarify if TET could represent a putative biomarker of psychostimulant use and if DNMT inhibition could have therapeutic potential.
The complexity of cyberattacks in Cyber-Physical Systems (CPSs) calls for a mechanism that can evaluate critical infrastructures’ operational behaviour and security without affecting the operation of live systems. In this regard, Digital Twins (DTs) provide actionable insights through monitoring, simulating, predicting, and optimizing the state of CPSs. Through the use cases, including system testing and training, detecting system misconfigurations, and security testing, DTs strengthen the security of CPSs throughout the product lifecycle. However, such benefits of DTs depend on an assumption about data integrity and security. Data trustworthiness becomes more critical while integrating multiple components among different DTs owned by various stakeholders to provide an aggregated view of the complex physical system. This article envisions a blockchain-based DT framework as Trusted Twins for Securing Cyber-Physical Systems (TTS-CPS). With the automotive industry as a CPS use case, we demonstrate the viability of the TTS-CPS framework through a proof of concept. To utilize reliable system specification data for building the process knowledge of DTs, we ensure the trustworthiness of data-generating sources through Integrity Checking Mechanisms (ICMs). Additionally, Safety and Security (S&S) rules evaluated during simulation are stored and retrieved from the blockchain, thereby establishing more understanding and confidence in the decisions made by the underlying systems. Finally, we perform formal verification of the TTS-CPS.
Purpose To assess whether intraabdominal hypertension (IAH) may influence kidney failure as well as mortality. Methods This post-hoc analysis of two databases (IROI and iSOFA study) tested the independent association between IAH and kidney failure. Mortality was assessed using four prespecified groups (IAH present, kidney failure present, IAH and kidney failure present and no IAH or kidney failure present). Results Of 825 critically ill patients, 302 (36.6%) developed kidney failure and 192 (23.7%) died during the first 90 days. Only ‘Cumulative days with IAH grade II or more’ was significantly associated with kidney failure (OR 1.29 (1.08–1.55), p = 0.003) while ‘cumulative days with IAH grade I or more’ (p = 0.135) or highest daily IAP (p = 0.062) was not. IAH combined with kidney failure was independently associated with 90-day mortality (OR 2.20 (1.20–4.05), p = 0.011), which was confirmed for higher grades of IAH (grade II or more) alone (OR 2.14 (1.07–4.30), p = 0.032) and combined with kidney failure (OR 3.25 (1.72–6.12), p < 0.001). Conclusions This study suggest that duration as well as higher grades of IAH are associated with kidney failure and may increase mortality.
The Northern pike (Esox lucius) is an important predator in freshwater and brackish water environments. In the Baltic Sea, Northern pike follows isolation by distance pattern across wide geographical scale. However, relatively little is known about the fine-scale population divergence and temporal genetic variation of Baltic pike, especially for populations inhabiting the eastern part of the Baltic Sea. Here, we characterize the population genetic structure of Northern pike and its temporal stability in six freshwater and one brackish water locations on the Island of Saaremaa (Estonia). To accomplish this, we collected 274 young-of-the-year (YOY) of two consecutive cohorts and 218 older specimens that were genotyped using ten microsatellite loci. Our results indicate a temporally stable population differentiation between geographically close locations and reduced diversity of the north-western Saaremaa populations. Furthermore, the correspondence analysis and a discriminant analysis of principal components showed a clear differentiation between north-western and the Gulf of Riga spawning grounds. Our findings support the idea that natal homing behavior, limited dispersal and facultative anadromy in Baltic pike likely promotes the existence of temporally stable genetic divergence among different populations at small geographical scale, representing an essential prerequisite for development of local adaptations. Thus, conservation, management and restoration efforts of coastal Baltic Sea pike should preserve the existing genetic differences between different populations and avoid actions, which potentially increase genetic homogenization.
Due to financial constraints, it can be expected that low-income groups may encounter transport poverty (e.g., limited travel mode options, low accessibility to workplaces) and have poor health conditions, therefore making them feel unsatisfied with commuting. However, few previous studies have examined this assumption. Using data derived from a face-to-face survey performed in 2019 in Chengdu (China), we aim to explore the association between income and commute satisfaction and particularly examine the mediating roles of transport poverty and health conditions in this association. Structural equation modeling is used to estimate both direct and indirect effects of income on commute satisfaction, leading to three major findings. First, due to limited access to cars, people with low incomes are more likely to choose public transit for commuting and indicate a high level of traffic congestion. Consequently, they tend to have long commute durations and are less likely to be satisfied with commuting. Second, low-income groups are more likely to have poor health conditions, which is another cause of their low commute satisfaction. Third, high-income groups are more likely to use private cars for commuting, which also leads to a high level of congestion, long commute durations, and low commute satisfaction.
Application of wood ash to forests can restore pools of phosphorus (P) and other nutrients, which are removed following whole tree harvesting. Yet, the mechanisms that affect the fate of ash-P in the organic layer are less well known. Previous research into the extent to which ash application leads to increased P solubility in the soil is contradictory. We combined synchrotron P K-edge XANES spectroscopy, µ-XRF microscopy, and chemical extractions to examine the speciation and solubility of P. We studied organic horizons of two long-term field experiments, Riddarhyttan (central Sweden), which had received 3, 6, and 9 Mg ash ha⁻¹, and Rödålund (northern Sweden), where 3 Mg ash ha⁻¹ had been applied alone or combined with N every-three years since 2003. At the latter site, we also determined P in aboveground tree biomass. Overall, the ash application increased P in the organic layer by between 6 and 28 kg P ha⁻¹, equivalent to 17–39 % of the initial P content in the applied ash. At Rödålund, there was 4.6 kg Ca-bound P ha⁻¹ (9.5 %) in the ash treatment compared to 1.6 kg ha⁻¹ in the ash + N treatment and < 0.4 kg ha⁻¹ in the N treatment and the control. At Riddarhyttan, only the treatment with the highest ash dose had residual Ca-bound P (3.8 kg ha⁻¹). In contrast, the ash application increased Al-bound P (p < 0.001) with up to 15.6 kg P ha⁻¹. Moreover, the ash increased Olsen-P by up to two times. There was a strong relationship between the concentrations of Olsen-P and Al-bound P (R² = 0.83, p < 0.001) as well as Fe-bound P (R² = 0.74, p = 0.003), suggesting that the ash application resulted in an increased amount of relatively soluble P associated with hydroxy-Al and hydroxy-Fe compounds. Further, there was an 18 % increase in P uptake by trees in the ash treatment. By contrast, repeated N fertilization, with or without ash, reduced Olsen-P. The lower P extractability was concomitant with a 39 % increase in plant P uptake in the N treatment, which indicates elevated P uptake in response to higher N availability. Hence, the application of wood ash increased Al-bound P, easily available P, and P uptake. N fertilization, while also increasing tree P uptake, instead decreased easily available P and did not cause a shift in soil P speciation.
The boreal forest is an important global carbon (C) sink. Since low soil nitrogen (N) availability is commonly a key constraint on forest productivity, the prevalent view is that increased N input enhances its C sink-strength. This understanding however relies primarily on observations of increased aboveground tree biomass and soil C stock following N fertilization, whereas empirical data evaluating the effects on the whole ecosystem-scale C balance are lacking. Here we use a unique long-term experiment consisting of paired forest stands with eddy covariance measurements to explore the effect of ecosystem-scale N fertilization on the C balance of a managed boreal pine forest. We find that the annual C uptake (i.e. net ecosystem production, NEP) at the fertilized stand was 16 ± 2% greater relative to the control stand by the end of the first decade of N addition. Subsequently, the ratio of NEP between the fertilized and control stand remained at a stable level during the following five years with an average NEP to N response of 7 ± 1 g C per g N. Our study reveals that this non-linear response of NEP to long-term N fertilization was the result of a cross-seasonal feedback between the N-induced increases in both growing-season C uptake and subsequent winter C emission. We further find that one decade of N addition altered the sensitivity of ecosystem C fluxes to key environmental drivers resulting in divergent responses to weather patterns. Thus, our study highlights the need to account for ecosystem-scale responses to perturbations to improve our understanding of nitrogen-carbon-climate feedbacks in boreal forests.
Let X1,…,Xn\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$X_1,\ldots ,X_n$$\end{document} be an i.i.d. sample from symmetric stable distribution with stability parameter α\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document} and scale parameter γ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma$$\end{document}. Let φn\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varphi _n$$\end{document} be the empirical characteristic function. We prove a uniform large deviation inequality: given preciseness ϵ>0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\epsilon >0$$\end{document} and probability p∈(0,1)\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$p\in (0,1)$$\end{document}, there exists universal (depending on ϵ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\epsilon$$\end{document} and p but not depending on α\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document} and γ\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\gamma$$\end{document}) constant r¯>0\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\bar{r}>0$$\end{document} so that P(supu>0:r(u)≤r¯|r(u)-r^(u)|≥ϵ)≤p,\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$P\big (\sup _{u>0:r(u)\le \bar{r}}|r(u)-\hat{r}(u)|\ge \epsilon \big )\le p,$$\end{document}where r(u)=(uγ)α\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$r(u)=(u\gamma )^{\alpha }$$\end{document} and r^(u)=-ln|φn(u)|\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\hat{r}(u)=-\ln |\varphi _n(u)|$$\end{document}. As an applications of the result, we show how it can be used in estimation the unknown stability parameter α\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\alpha$$\end{document}.
The past decade has seen a shift in the way that minorities exert their influence in society. Where in previous decades the emphasis was on winning the hearts and minds of the population at large, a recent strategy has been to ignore general public discourse and only to target specific influential bodies. In this paper we use the example of transgender issues to analyse the socio-psychological dimensions of this approach. We show how some groups promoting these issues eschew a wider social discourse and debate in the mass media, and how their strategy rests on a self-construction as victims of the hetero-normative society, with a concomitant appeal to moral rather than factual argumentation. This is combined with a programme of aggressive challenge to opponents through social media, and sometimes direct action, which effectively closes discussion on the topic. We conclude that these methods have much in common with the oppressive politics of an upcoming fascist rule.
The increasing sense of urgency to transition to sustainable modes of consumption and production requires an understanding of social problem framings and processes of change. We examine how two conceptual frameworks, the Multi-level Perspective (MLP), a socio-technical transition theory, and Social Practice Approaches (SPA), contribute to understanding opportunities for social change. We share the results of a systematic literature review that seeks a better understanding of how these two approaches are co-employed. We first present quantifiable results from an analysis of 118 publications; we then focus on a qualitative analysis to investigate conceptual complementarities while recognizing their ontological differences. We find further entry points where the two approaches can be fruitfully combined, such as the study of vulnerable proto-practices, research on informal regimes, and the development of landscape- and supra-practice-level meanings. We conclude with recommendations on how to further operationalize the co-employment of MLP and SPA in sustainability transition studies.
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• Institute of Genomics
• Institute of Philosophy and Semiotics
• Institute of Exercise Biology and Physiotherapy
• Department of Geology
• Institute of Ecology and Earth Sciences
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