Browsing by Subject "OBJECTS"

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  • Novakovic, Bojan; Tsirvoulis, Georgios; Granvik, Mikael; Todovic, Ana (2017)
    We report the discovery of a new asteroid family among the dark asteroids residing in the Phocaea region the Tamara family. We make use of available physical data to separate asteroids in the region according to their surface reflectance properties, and establish the membership of the family. We determine the slope of the cumulative magnitude distribution of the family, and find it to be significantly steeper than the corresponding slope of all the asteroids in the Phocaea region. This implies that subkilometer dark Phocaeas are comparable in number to bright S-type objects, shedding light on an entirely new aspect of the composition of small Phocaea asteroids. We then use the Yarkovsky V-shape based method and estimate the age of the family to be 264 +/- 43Myr. Finally, we carry out numerical simulations of the dynamical evolution of the Tamara family. The results suggest that up to 50 Tamara members with absolute magnitude H <19.4 may currently be found in the near-Earth region. Despite their relatively small number in the near-Earth space, the rate of Earth impacts by small, dark Phocaeas is non-negligible.
  • Hosoya, Haruo; Hyvärinen, Aapo (2017)
    Experimental studies have revealed evidence of both parts-based and holistic representations of objects and faces in the primate visual system. However, it is still a mystery how such seemingly contradictory types of processing can coexist within a single system. Here, we propose a novel theory called mixture of sparse coding models, inspired by the formation of category-specific subregions in the inferotemporal (IT) cortex. We developed a hierarchical network that constructed a mixture of two sparse coding submodels on top of a simple Gabor analysis. The submodels were each trained with face or non-face object images, which resulted in separate representations of facial parts and object parts. Importantly, evoked neural activities were modeled by Bayesian inference, which had a top-down explaining-away effect that enabled recognition of an individual part to depend strongly on the category of the whole input. We show that this explaining-away effect was indeed crucial for the units in the face submodel to exhibit significant selectivity to face images over object images in a similar way to actual face-selective neurons in the macaque IT cortex. Furthermore, the model explained, qualitatively and quantitatively, several tuning properties to facial features found in the middle patch of face processing in IT as documented by Freiwald, Tsao, and Livingstone (2009). These included, in particular, tuning to only a small number of facial features that were often related to geometrically large parts like face outline and hair, preference and anti-preference of extreme facial features (e.g., very large/small inter-eye distance), and reduction of the gain of feature tuning for partial face stimuli compared to whole face stimuli. Thus, we hypothesize that the coding principle of facial features in the middle patch of face processing in the macaque IT cortex may be closely related to mixture of sparse coding models.
  • Saajasto, Mika; Harju, Jorma; Juvela, Mika; Tie, Liu; Zhang, Qizhou; Liu, Sheng-Yuan; Hirano, Naomi; Wu, Yuefang; Kim, Kee-Tae; Tatematsu, Kenichi; Wang, Ke; Thompson, Mark (2019)
    Context. We present molecular line and dust continuum observations of a Planck-detected cold cloud, G074.11+00.11. The cloud consists of a system of curved filaments and a central star-forming clump. The clump is associated with several infrared sources and H2O maser emission. Aims. We aim to determine the mass distribution and gas dynamics within the clump to investigate if the filamentary structure seen around the clump repeats itself on a smaller scale, and to estimate the fractions of mass contained in dense cores and filaments. The velocity distribution of pristine dense gas can be used to investigate the global dynamical state of the clump, the role of filamentary inflows, filament fragmentation, and core accretion. Methods. We used molecular line and continuum observations from single dish observatories and interferometric facilities to study the kinematics of the region. Results. The molecular line observations show that the central clump may have formed as a result of a large-scale filament collision. The central clump contains three compact cores. Assuming a distance of 2.3 kpc, based on Gaia observations and a three-dimensional extinction method of background stars, the mass of the central clump exceeds 700 M-circle dot, which is roughly similar to 25% of the total mass of the cloud. Our virial analysis suggests that the central clump and all identified substructures are collapsing. We find no evidence for small-scale filaments associated with the cores. Conclusions. Our observations indicate that the clump is fragmented into three cores with masses in the range [10, 50] M-circle dot and that all three are collapsing. The presence of an H2O maser emission suggests active star formation. However, the CO lines show only weak signs of outflows. We suggest that the region is young and any processes leading to star formation have just recently begun.
  • Olofson, Anders O.; Lindberg, J. Ola; Pedersen, Alex Young; Arstorp, Ann-Thérèse; Dalsgaard, Christian; Einum, Even; Caviglia, Francesco; Ilomäki, Liisa; Veermans, Marjaana; Häkkinen, Päivi; Willermark, Sara (2021)
    This paper explores policy related to digital competence and the digitalisation of Nordic K-12 schools. Anchored in some key transnational policies on digital competence, it describes some current Nordic movements in the national policies of Denmark, Finland, Norway and Sweden. The concept of boundary objects is used as an analytical lens, for understanding digital competence as a plastic and temporal concept that can be used to discuss the multi-dimensional translation of this concept in these Nordic countries. The paper ends with a discussion of the potential to view digital competence as a unifying boundary object that, with its plasticity, temporality and n-dimensionality, can show signs of common Nordic efforts in the K-12 school policy.
  • Fedorets, Grigori; Granvik, Mikael; Jones, R. Lynne; Jurić, Mario; Jedicke, Robert (2020)
    Earth’s temporarily-captured orbiters (TCOs) are a sub-population of near-Earth objects (NEOs). TCOs can provide constraints for NEO population models in the 1–10-metre-diameter range, and they are outstanding targets for in situ exploration of asteroids due to a low requirement on Δv. So far there has only been a single serendipitous discovery of a TCO. Here we assess in detail the possibility of their discovery with the upcoming Large Synoptic Survey Telescope (LSST), previously identified as the primary facility for such discoveries. We simulated observations of TCOs by combining a synthetic TCO population with an LSST survey simulation. We then assessed the detection rates, detection linking and orbit computation, and sources for confusion. Typical velocities of detectable TCOs will range from 1∘/day to 50∘/day, and typical apparent V magnitudes from 21 to 23. Potentially-hazardous asteroids have observational characteristics similar to TCOs, but the two populations can be distinguished based on their orbits with LSST data alone. We predict that a TCO can be discovered once every year with the baseline moving-object processing system (MOPS). The rate can be increased to one TCO discovery every two months if tools complementary to the baseline MOPS are developed for the specific purpose of discovering these objects.
  • Jedicke, Robert; Bolin, Bryce T:; Bottke, William F.; Chyba, Monique; Fedorets, Grigori; Granvik, Mikael Matias Sebastian; Jones, R. Lynne; Urrutxua, Hodei (2018)
    Twelve years ago the Catalina Sky Survey discovered Earth's first known natural geocentric object other than the Moon, a few-meter diameter asteroid designated 2006 RH120. Despite significant improvements in ground-based telescope and detector technology in the past decade the asteroid surveys have not discovered another temporarily-captured orbiter (TCO; colloquially known as minimoons) but the all-sky fireball system operated in the Czech Republic as part of the European Fireball Network detected a bright natural meteor that was almost certainly in a geocentric orbit before it struck Earth's atmosphere. Within a few years the Large Synoptic Survey Telescope (LSST) will either begin to regularly detect TCOs or force a re-analysis of the creation and dynamical evolution of small asteroids in the inner solar system. The first studies of the provenance, properties, and dynamics of Earth's minimoons suggested that there should be a steady state population with about one 1- to 2-m diameter captured objects at any time, with the number of captured meteoroids increasing exponentially for smaller sizes. That model was then improved and extended to include the population of temporarily-captured flybys (TCFs), objects that fail to make an entire revolution around Earth while energetically bound to the Earth-Moon system. Several different techniques for discovering TCOs have been considered but their small diameters, proximity, and rapid motion make them challenging targets for existing ground-based optical, meteor, and radar surveys. However, the LSST's tremendous light gathering power and short exposure times could allow it to detect and discover many minimoons. We expect that if the TCO population is confirmed, and new objects are frequently discovered, they can provide new opportunities for (1) studying the dynamics of the Earth-Moon system, (2) testing models of the production and dynamical evolution of small asteroids from the asteroid belt, (3) rapid and frequent low delta-v missions to multiple minimoons, and (4) evaluating in-situ resource utilization techniques on asteroidal material. Here we review the past decade of minimoon studies in preparation for capitalizing on the scientific and commercial opportunities of TCOs in the first decade of LSST operations.
  • Fedorets, Grigori; Micheli, Marco; Jedicke, Robert; Naidu, Shantanu P.; Farnocchia, Davide; Granvik, Mikael; Moskovitz, Nicholas; Schwamb, Megan E.; Weryk, Robert; Wierzchos, Kacper; Christensen, Eric; Pruyne, Theodore; Bottke, William F.; Ye, Quanzhi; Wainscoat, Richard; Devogele, Maxime; Buchanan, Laura E.; Djupvik, Anlaug Amanda; Faes, Daniel M.; Fohring, Dora; Roediger, Joel; Seccull, Tom; Smith, Adam B. (2020)
    We report on our detailed characterization of Earth's second known temporary natural satellite, or minimoon, asteroid 2020 CD3. An artificial origin can be ruled out based on its area-to-mass ratio and broadband photometry, which suggest that it is a silicate asteroid belonging to the S or V complex in asteroid taxonomy. The discovery of 2020 CD3 allows for the first time a comparison between known minimoons and theoretical models of their expected physical and dynamical properties. The estimated diameter of 1.2(-0.2)(+0.4) m and geocentric capture approximately a decade after the first known minimoon, 2006.RH120, are in agreement with theoretical predictions. The capture duration of 2020 CD3 of at least 2.7 yr is unexpectedly long compared to the simulation average, but it is in agreement with simulated minimoons that have close lunar encounters, providing additional support for the orbital models. 2020 CD3's atypical rotation period, significantly longer than theoretical predictions, suggests that our understanding of meter-scale asteroids needs revision. More discoveries and a detailed characterization of the population can be expected with the forthcoming Vera C. Rubin Observatory Legacy Survey of Space and Time.
  • Pöntinen, M.; Granvik, M.; Nucita, A. A.; Conversi, L.; Altieri, B.; Auricchio, N.; Bodendorf, C.; Bonino, D.; Brescia, M.; Capobianco, V.; Carretero, J.; Carry, B.; Castellano, M.; Cledassou, R.; Congedo, G.; Corcione, L.; Cropper, M.; Dusini, S.; Frailis, M.; Franceschi, E.; Fumana, M.; Garilli, B.; Grupp, F.; Hormuth, F.; Israel, H.; Jahnke, K.; Kermiche, S.; Kitching, T.; Kohley, R.; Kubik, B.; Kunz, M.; Laureijs, R.; Lilje, P. B.; Lloro, I.; Maiorano, E.; Marggraf, O.; Massey, R.; Meneghetti, M.; Meylan, G.; Moscardini, L.; Padilla, C.; Paltani, S.; Pasian, F.; Pires, S.; Polenta, G.; Raison, F.; Roncarelli, M.; Rossetti, E.; Saglia, R.; Schneider, P.; Secroun, A.; Serrano, S.; Sirri, G.; Tereno, I.; Toledo-Moreo, R.; Valenziano, L.; Wetzstein, M.; Zoubian, J. (2020)
    Context. The ESA Euclid space telescope could observe up to 150 000 asteroids as a side product of its primary cosmological mission. Asteroids appear as trailed sources, that is streaks, in the images. Owing to the survey area of 15 000 square degrees and the number of sources, automated methods have to be used to find them. Euclid is equipped with a visible camera, VIS (VISual imager), and a near-infrared camera, NISP (Near-Infrared Spectrometer and Photometer), with three filters.Aims. We aim to develop a pipeline to detect fast-moving objects in Euclid images, with both high completeness and high purity.Methods. We tested the StreakDet software to find asteroids from simulated Euclid images. We optimized the parameters of StreakDet to maximize completeness, and developed a post-processing algorithm to improve the purity of the sample of detected sources by removing false-positive detections.Results.StreakDet finds 96.9% of the synthetic asteroid streaks with apparent magnitudes brighter than 23rd magnitude and streak lengths longer than 15 pixels (10 arcsec h(-1)), but this comes at the cost of finding a high number of false positives. The number of false positives can be radically reduced with multi-streak analysis, which utilizes all four dithers obtained by Euclid.Conclusions.StreakDet is a good tool for identifying asteroids in Euclid images, but there is still room for improvement, in particular, for finding short (less than 13 pixels, corresponding to 8 arcsec h(-1)) and/or faint streaks (fainter than the apparent magnitude of 23).
  • Malinen, J.; Montier, L.; Montillaud, J.; Juvela, M.; Ristorcelli, I.; Clark, S. E.; Berne, O.; Bernard, J.-Ph.; Pelkonen, V.-M.; Collins, D. C. (2016)
    The nearby cloud L1642 is one of only two known very high latitude (b| > 30 deg) clouds actively forming stars. It is a rare example of star formation in isolated conditions, and can reveal important details of star formation in general, e.g. of the effect of magnetic fields. We compareHerschel dust emission structures and magnetic field orientation revealed byPlanck polarization maps in L1642. The high-resolution (similar to 20 arcsec)Herschel data reveal a complex structure including a dense, compressed central clump, and low-density striations. ThePlanck polarization data (at 10 arcmin resolution) reveal an ordered magnetic field pervading the cloud and aligned with the surrounding striations. There is a complex interplay between the cloud structure and large-scale magnetic field. This suggests that the magnetic field is closely linked to the formation and evolution of the cloud. CO rotational emission confirms that the striations are connected with the main clumps and likely to contain material either falling into or flowing out of the clumps. There is a clear transition from aligned to perpendicular structures approximately at a column density ofN(H) = 1.6 x 10(21) cm(-2). Comparing theHerschel maps with thePlanck polarization maps shows the close connection between the magnetic field and cloud structure even in the finest details of the cloud.
  • Telkanranta, Helena; Valros, Anna (2020)
    In barren environments of commercial farms, pig often redirect their rooting and chewing behaviours at other pigs, which can lead to tail biting. When materials such as straw are provided, the quantity is usually too small to have an effect. The aim of this study was to test whether small provisions of straw and species-relevant point- source objects would have an additive effect in reducing pen-mate manipulation. The animals were 167 gilts with undocked tails on a commercial farm in Finland, housed in 12-m2 pens with partly slatted floors, on average 7 pigs/pen. Liquid feed and 20 g/pig of long straw were provided once a day. The pigs had continuous access to suspended objects: in each control pen (N =12), a 40cm ×10cm ×2 cm piece of commercially sourced wooden board and a 60-cm metal chain, and in each experimental pen (N =12), an 80-cm piece and two 40-cm pieces of birch trees with a diameter of 5–7 cm, harvested 1 month earlier. After 2 months of exposure, frequencies of pig- and object-directed manipulation before and after consuming the feed and straw were recorded by continuous observation on video. Pre-consumption pig-directed manipulation did not differ between the treatments (means: 39.3 events/pig/hour (SD =11.7) in the experimental pens and 42.1 events/pig/hour (SD =12.1) in the control pens; t =-0.6, df =21, P >0.1), but post-consumption manipulation was significantly lower in frequency in the experimental treatment (means: 31.5 events/pig/hour (SD =10.4) in the experimental pens and 41.0 events/ pig/hour (SD =8.6) in the control pens; t =2.4, df =21, P <0.05). Object-directed manipulation was higher in the experimental treatment both pre- and post-consumption (pre-consumption medians: 9.7 events/pig/hour (min =2.0, max =14.9) in the experimental pens and 3.1 events/pig/hour (min =0.9, max =13.7) in the control pens (U =18.5, P <0.01); post-consumption means: 9.2 events/hour/pig (SD =2.7) in the experimental pens and 4.8 events/pig/hour (SD =2.0) in the control pens (t =4.5, df =20, P <0.001). It was concluded that the experimental objects with improved material, quantity, shape and location had an additive effect with straw in reducing pen-mate manipulation, whereas objects ordinarily used on the farm had no beneficial effect. Further research is needed on the effects of the odour, taste and consistency of optimal objects.
  • Savastano, Stefano; Amendola, Luca; Rubio, Javier; Wetterich, Christof (2019)
    We argue that primordial dark matter halos could be generated during radiation domination by long-range attractive forces stronger than gravity. In this paper, we derive the conditions under which these structures could dominate the dark matter content of the Universe while passing microlensing constraints and cosmic microwave background energy injection bounds. The dark matter particles would be clumped in objects in the solar mass range with typical sizes of the order of the solar system. Consequences for direct dark matter searches are important.
  • Hietanen, Joel; Murray, Jeff B.; Sihvonen, Antti; Tikkanen, Henrikki (2020)
    Authenticity has often been considered to be a key theme in contemporary consumer culture. One of its manifestations is how branded market offerings can maintain authentic meanings, especially in a market increasingly saturated with counterfeit substitutes. By following a Baudrillardian perspective, we focus on fashion objects in the "branded luxury" category to problematize the sanctity of the authentic/counterfeit distinction. We argue that marketing literature generally attempts to normatively maintain and impose the distinction in ways that obscure the complexities of this conceptual interplay. We posit that instead of normative accounts that attempt to sanctify the extant orders of global capitalist markets, literature on luxury consumption should instead recognize the excess of meaning in the semiotic interplay of commodified authentic/counterfeit meanings. Any view of morality in luxury consumption should thus recognize "ambivalence" and "seduction" as its intensive qualities.
  • Granvik, Mikael; Vaubaillon, Jeremie; Jedicke, Robert (2012)
  • Mäki, Tarja; Kerosuo, Hannele; Koskenvesa, Anssi (2020)
    This study examines the learning processes of the adoption of the Last Planner System (LPS) and mechanisms of learning indicating the successes and failures of their establishment in three organisations. The organisations under study are a public building agency, an engineering office, and a construction company. One practice-based methodology by Engeström and Sannino of organisational learning based on the theory of expansive learning was applied in the analysis. The ethnographic research data included the observation of LPS adoption processes and the interviews of the participants. This study links the epistemic learning actions of the theory of expansive learning to the adoption process of LPS. It also reveals the mechanisms that indicate the success or failure of the adoption process. A successful adoption process seems to require strong ownership, enough time, resources, and opportunities for learning together in practical project work, and the combination of top-down and bottom-up approaches.