Articles

Recent Submissions

  • Öhman, J.; Harjola, Veli-Pekka; Karjalainen, P.; Lassus, Johan (2018)
  • Helsingin yliopisto, Geotieteiden ja maantieteen osasto; Helsingin yliopisto, Geotieteiden ja maantieteen osasto; Bäcklund, Satu Pia Marianne; Häkli, Jouni; Schulman, Harry Olavi; (Tampere University Press, 2017)
  • Pooch, Fabian; Sliepen, Marjolein; Svedström, Kirsi J.; Korpi, Antti; Winnik, Francoise M.; Tenhu, Heikki (2018)
    Miscible block copolymers (BCPs) are rarely studied. When one or both components of such BCPs are semi-crystalline polymers, strong effects on the crystallization behavior can be expected. We present a study of 18 miscible BCPs comprised of poly(lactide) (PLLA, semi-crystalline and PDLLA, amorphous) and poly(2-isopropyl-2-oxazoline) (PiPOx, semi-crystalline) with PiPOx volume fractions of 0.14 <phi(PiPOx) <0.82. All BCPs exhibit a single glass transition and form a homogeneous melt. Mixing has a plasticizing effect on PiPOx and increases its crystallization rates (DSC). In contrast, the crystallization rates of PLLA are dramatically reduced, or in most cases entirely prevented. During isothermal crystallization at 130 degrees C, the crystallization rates of the BCPs were inverted in comparison with those of the parent homopolymers. Crystallization drives the BCPs to phase separate and the formed crystalline structure is that of the parent homopolymers. The fast crystallization of PiPOx confines the observed superstructure. The BCPs were studied on multiple length scales - from the atomic level (WAXS, IR spectroscopy) to the meso level (AFM, SAXS) and the macroscopic superstructure (polarized optical microscopy). A mechanism of the structure evolution is presented.
  • Vidilaseris, Keni; Kellosalo, Juho; Goldman, Adrian (2018)
    Membrane-bound pyrophosphatases (mPPases) are homodimeric integral membrane proteins that hydrolyse pyrophosphate into orthophosphates coupled to the active transport of protons or sodium ions across membranes. They occur in bacteria, archaea, plants, and protist parasites. As they are essential in protist parasites and there are no homologous proteins in animals and humans, these enzymes represent an excellent drug target for treating protistal diseases. Experimental screening to find drug candidates is an important step to discover new hit compounds. For that, a cheap, simple, and robust assay is needed. Here we report the application of the molybdenum blue reaction method for a medium throughput microplate activity assay of the hyperthermophilic bacterium Thermotoga maritima mPPase and the possible application of the assay to screen inhibitors of membrane-bound pyrophosphatases.
  • Suarez, Anna; Lahti, Jari; Czamara, Darina; Lahti-Pulkkinen, Marius; Girchenko, Polina; Andersson, Sture; Strandberg, Timo E; Reynolds, Rebecca M; Kajantie, Eero; Binder, Elisabeth B; Raikkonen, Katri (BioMed Central, 2018)
    Abstract Background Molecular aging biomarkers, such as epigenetic age predictors, predict risk factors of premature aging, and morbidity/mortality more accurately than chronological age in middle-aged and elderly populations. Yet, it remains elusive if such biomarkers are associated with aging-related outcomes earlier in life when individuals begin to diverge in aging trajectories. We tested if the Horvath epigenetic age predictor is associated with pubertal, neuroendocrine, psychiatric, and cognitive aging-related outcomes in a sample of 239 adolescents, 11.0–13.2 years-old. Results Each year increase in epigenetic age acceleration (AA) was associated with 0.06 SD units higher weight-for-age, 0.08 SD units taller height-for-age, -0.09 SD units less missed from the expected adult height, 13 and 16% higher odds, respectively, for each stage increase in breast/genitals development on the Tanner Staging Questionnaire and pubertal stage on the Pubertal Development Scale, 4.2% higher salivary cortisol upon awakening, and 18 to 34% higher odds for internalizing and thought problems on the Child Behavior Checklist (p values <  0.045). AA was not significantly associated with cognition. Conclusions Our findings suggest that already in adolescence, AA is associated with physiological age acceleration, which may index risk of earlier aging. AA may identify individuals for preventive interventions decades before aging-related diseases become manifest.
  • Pöyry, Essi Ilona; Laaksonen, Salla-Maaria; Kekkonen, Arto Ilmari; Pääkkönen, Juho Ilmari (University of Hawai'i at Manoa, 2018)
    Discussion topics go sometimes viral in social media without a seemingly coherent pattern. Existing literature shows these discussions can reach a very high level, but, notably, they prevail to varying degrees. This paper investigates the anatomy of viral social media events using a dataset of 960 viral social media discussion topics that have been identified by an algorithm from a variety of social media sources over two years’ time. A negative binomial regression shows that the average daily amount and the relative change in the daily amount of social media platforms at which the event has been discussed has a positive effect on the duration of the event. Average or relative amount of posts or authors has no or very little effect on event duration. The results suggest that viral social media events last longer when people using different social media platforms get exposed to them. This finding contributes to the literature on social media events, virality, and information diffusion.
  • Wallin, Antti; Leino, Helena; Jokinen, Ari; Laine, Markus; Tuomisaari, Johanna; Backlund, Pia (2018)
    Urban strategies, representing stories of possible futures, often intervene in already established local communities and therefore call for a considerate urban intervention. This article utilises the ideas of Henri Lefebvre's socially produced space and of literature on stories involved in planning. Our empirical example tells a story of urban densification aspirations for an inner-city neighbourhood in Tampere, Finland. By combining the interviews of local people and planners with policy documents, we argue that planners' stories pay too little attention to the place and to local stories. Planners' abstract visions of the future and local stories building on lived experiences both draw meanings from the same place but have very different intentions. In our case, the consultation of the project started out wrong because the planners neglected a neighbourhood thick in symbolic meanings and the local stories' power in resistance. By understanding the place as polyphonic in its foundation, planners could learn about the symbolic elements and reasons for people's place attachment, and thus end up re-writing the place together. Urban interventions such as urban densification should connect to the place as part of its polyphonic historical continuum and acknowledge the residents' place attachments.
  • Raisanen, Sari; Hogue, Carol J. R.; Laine, Katariina; Kramer, Michael R.; Gissler, Mika; Heinonen, Seppo (2018)
    ObjectiveTo examine the effect of pregnancy history on the risk of stillbirth. MethodsIn a population-based cross-sectional study, data were reviewed from all women aged at least 20years with singleton pregnancies in Finland between 2000 and 2010. The primary outcomestillbirthwas defined as fetal death after 22 gestational weeks or death of a fetus weighing at least 500g. ResultsAmong 604047 singleton pregnancies, the prevalence of stillbirth was 3.17 per 1000 deliveries. Prevalence was lowest for multiparous women without previous pregnancy loss after adjusting for major pregnancy complications associated with stillbirth (placenta previa, placental abruption, and pre-eclampsia) and other confounders. Relative to these women, stillbirth prevalence was higher among multiparous women with previous spontaneous abortion and/or stillbirth (adjusted odds ratio [aOR] 1.20, 95% confidence interval [CI] 1.05-1.36), nulliparous women with no previous pregnancy loss (aOR 1.23, 95% CI 1.10-1.38), and nulliparous women with prior spontaneous abortion (aOR 1.43, 95% CI 1.18-1.74). ConclusionPrevious pregnancy loss was found to be an independent risk factor for stillbirth, irrespective of the number of prior deliveries. Spontaneous abortion assessed as a part of pregnancy history was found to be an independent risk factor for stillbirth.
  • Kuntner, Matjaz; Rudolf, Elena; Cardoso, Pedro (2017)
  • Miettinen, O. (2018)
    Context. Filamentary molecular clouds, such as many of the infrared dark clouds (IRDCs), can undergo hierarchical fragmentation into substructures (clumps and cores) that can eventually collapse to form stars. Aims. We aim to determine the occurrence of fragmentation into cores in the clumps of the filamentary IRDC G304.74 + 01.32 (hereafter, G304.74). We also aim to determine the basic physical characteristics (e.g. mass, density, and young stellar object (YSO) content) of the clumps and cores in G304.74. Methods. We mapped the G304.74 filament at 350 mu m using the Submillimetre APEX Bolometer Camera (SABOCA) bolometer. The new SABOCA data have a factor of 2.2 times higher resolution than our previous Large APEX BOlometer CAmera (LABOCA) 870 mu m map of the cloud (9 '' vs. 19 ''.86). We also employed the Herschel far-infrared (IR) and submillimetre, andWide-field Infrared Survey Explorer (WISE) IR imaging data available for G304.74. The WISE data allowed us to trace the IR emission of the YSOs associated with the cloud. Results. The SABOCA 350 mu m data show that G304.74 is composed of a dense filamentary structure with a mean width of only 0.18 +/- 0.05 pc. The percentage of LABOCA clumps that are found to be fragmented into SABOCA cores is 36% +/- 16%, but the irregular morphology of some of the cores suggests that this multiplicity fraction could be higher. The WISE data suggest that 65% +/- 18% of the SABOCA cores host YSOs. The mean dust temperature of the clumps, derived by comparing the Herschel 250, 350, and 500 mu m flux densities, was found to be 15.0 +/- 0.8 K. The mean mass, beam-averaged H-2 column density, and H2 number density of the LABOCA clumps are estimated to be 55 +/- 10 M-circle dot, (2.0 +/- 0.2) x 10(22) cm(-2), and (3.1 +/- 0.2) x 10(4) cm(-3). The corresponding values for the SABOCA cores are 29 +/- 3 M-circle dot, (2.9 +/- 0.3) x 10(22) cm(-2), and (7.9 +/- 1.2) x 10(4) cm(-3). The G304.74 filament is estimated to be thermally supercritical by a factor of greater than or similar to 3.5 on the scale probed by LABOCA, and by a factor of greater than or similar to 1.5 for the SABOCA filament. Conclusions. Our data strongly suggest that the IRDC G304.74 has undergone hierarchical fragmentation. On the scale where the clumps have fragmented into cores, the process can be explained in terms of gravitational Jeans instability. Besides the filament being fragmented, the finding of embedded YSOs in G304.74 indicates its thermally supercritical state, although the potential non-thermal (turbulent) motions can render the cloud a virial equilibrium system on scale traced by LABOCA. The IRDC G304.74 has a seahorse-like morphology in the Herschel images, and the filament appears to be attached by elongated, perpendicular striations. This is potentially evidence that G304.74 is still accreting mass from the surrounding medium, and the accretion process can contribute to the dynamical evolution of the main filament. One of the clumps in G304.74, IRAS 13039-6108, is already known to be associated with high-mass star formation, but the remaining clumps and cores in this filament might preferentially form low and intermediate-mass stars owing to their mass reservoirs and sizes. Besides the presence of perpendicularly oriented, dusty striations and potential embedded intermediate-mass YSOs, G304.74 is a relatively nearby (d similar to 2.5 kpc) IRDC, which makes it a useful target for future star formation studies. Owing to its observed morphology, we propose that G304.74 could be nicknamed the Seahorse Nebula.
  • Louhivuori, Lauri M.; Turunen, Pauli M.; Louhivuori, Verna; Yellapragada, Venkatram; Nordstrom, Tommy; Uhlen, Per; Akerman, Karl E. (2018)
    Radial glial cells play an essential role through their function as guides for neuronal migration during development. Disruption of metabotropic glutamate receptor 5 (mGluR5) function retards the growth of radial glial processes in vitro. Neuregulins (NRG) are activated by proteolytic cleavage and regulate (radial) glial maintenance via ErbB3/ErbB4 receptors. We show here that blocking ErbB4 disrupts radial process extension. Soluble NRG acting on ErbB4 receptors is able to promote radial process extension in particular where process elongation has been impeded by blockade of mGluR5, the nonselective cation channel canonical transient receptor potential 3 (TRPC3), or matrix metalloproteases (MMP). NRG does not restore retarded process growth caused by ErbB4 blockade. Stimulation of muscarinic receptors restores process elongation due to mGluR5 blockade but not that caused by TRPC3, MMP or ErbB4 blockade suggesting that muscarinic receptors can replace mGluR5 with respect to radial process extension. Additionally, NRG/ErbB4 causes Ca2+ mobilization in a population of cells through cooperation with ErbB1 receptors. Our results indicate that mGluR5 promotes radial process growth via NRG activation by a mechanism involving TRPC3 channels and MMPs. Thus neurotransmitters acting on G-protein coupled receptors could play a central role in the maintenance of the radial glial scaffold through activation of NRG/ErbB4 signaling.
  • Yirdaw, Eshetu; Monge, Adrian (2018)
    There is ambiguity in the use of the terms enclosure and exclosure in describing the passive method used for the restoration of degraded ecosystems. We argue that in the context of ecological restoration, the term enclosure is generally more appropriate to use than exclosure. Unlike exclosure, the term enclosure focuses on the degraded area to be restored, does not exclude selective permeability of external factors, and potentially accommodates local people's livelihood needs. However, the term exclosure is appropriate to use in the case of experimental exclosures or management of restoration sites which explicitly exclude specific disturbance factors.
  • Purisha, Zenith; Rimpeläinen, Juho; Bubba, Tatiana; Siltanen, Samuli (2018)
    Tomographic reconstruction is an ill-posed inverse problem that calls for regularization. One possibility is to require sparsity of the unknown in an orthonormal wavelet basis. This, in turn, can be achieved by variational regularization, where the penalty term is the sum of the absolute values of the wavelet coefficients. The primal-dual fixed point algorithm showed that the minimizer of the variational regularization functional can be computed iteratively using a soft-thresholding operation. Choosing the soft-thresholding parameter mu > 0 is analogous to the notoriously difficult problem of picking the optimal regularization parameter in Tikhonov regularization. Here, a novel automatic method is introduced for choosing mu, based on a control algorithm driving the sparsity of the reconstruction to an a priori known ratio of nonzero versus zero wavelet coefficients in the unknown.
  • Yagmurlu, Bengi; Zhang, Wenzhong; Avdibegovic, Dzenita; Regadio, Mercedes; Koivula, Risto Tapio; Dittrich, Carsten; Binnemans, Koen; Friedrich, Bernd (ALTA, 2018)
  • Koponen, Lari M.; Nieminen, Jaakko O.; Ilmoniemi, Risto J. (2018)
    AbstractBackground Transcranial magnetic stimulation (TMS) is a non-invasive brain stimulation method: a magnetic field pulse from a TMS coil can excite neurons in a desired location of the cortex. Conventional TMS coils cause focal stimulation underneath the coil centre; to change the location of the stimulated spot, the coil must be moved over the new target. This physical movement is inherently slow, which limits, for example, feedback-controlled stimulation. Objective To overcome the limitations of physical TMS coil movement by introducing electronic targeting. Methods We propose electronic stimulation targeting using a set of large overlapping coils and introduce a matrix-factorisation-based method to design such sets of coils. We built one such device and demonstrated the electronic stimulation targeting in vivo. Results The demonstrated two-coil transducer allows translating the stimulated spot along a 30-mm line segment in the cortex; with five coils, a target can be selected from within a region of the cortex and stimulated in any direction. Thus, far fewer coils are required by our approach than by previously suggested ones, none of which have resulted in practical devices. Conclusion Already with two coils, we can adjust the location of the induced electric field maximum along one dimension, which is sufficient to study, for example, the primary motor cortex.