997 resultados para dark matter simulations


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Pro gradu -tutkielma käsittelee afroamerikkalaisen puhekielen (African American Vernacular English, AAVE) käyttöä kolmen englanninkielisen romaanin dialogissa ja suomen yleispuhekielen käyttöä romaanien käännöksissä. Tutkimus on pääasiassa kvantitatiivinen ja deskriptiivinen. Romaanit ovat Stephen Kingin The Dark Tower II: The Drawing of the Three (1987) (Musta torni 2, Kolme korttia pakasta 2005, suom. Kari Salminen), John Grishamin A Time to Kill (1989) (On aika tappaa 1994, suom. Kimmo Linkama) ja Sapphiren Push (1996) (Precious – harlemilaistytön tarina 2010, suom. Kristiina Drews). Alkukielisten romaanien osalta Grisham ja Sapphire suosivat lauseopillisia kielenpiirteitä, kun taas King on suosinut äänteellisiä. Sen sijaan käännöksissä piirteistä yleisimpiä ovat äänteelliset ja harvinaisimpia lauseopilliset. Vaikka käännöksissä sanastolliset piirteet ovat taajaan esiintyviä, äänteellisiä piirteitä esiintyy niitä enemmän. Poikkeuksena on On aika tappaa, jossa sanastollisia piirteitä esiintyy enemmän kuin äänteellisiä. Tulos eroaa Sampo Nevalaisen vuonna 2003 tekemästä tutkimuksesta, jossa hän sai selville, että käännöksissä käytetyt piirteet olivat enimmäkseen sanastollisia, kun taas alun perin suomeksi kirjoitetussa kaunokirjallisuudessa puhekielisyyden vaikutelma saatiin aikaan pääasiassa äänteellisin keinoin. Mahdollinen selitys tässä tutkimuksessa havaitulle erolle on se, että kahdessa romaanissa esiintyvä leimallinen AAVEn käyttö on saanut kääntäjät käyttämään samanlaisia strategioita kuin suomalaiset kirjailijat murretta kirjoittaessaan.

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Tässä kandidaatintyössä vertailtiin SolidWorks Simulations ja Femap FE-analyysiohjelmien tuottamia tuloksia. Vertailu suoritettiin yksinkertaisten RHS-putkipalkkien mallinnuksen avulla. Mallinnuksessa käytettiin viittä erilaista kuormitustapausta, jotka sisälsivät mm. taivutus-, vääntö- ja jännityskeskittymätarkastelut. Ohjelmien tuottamia tuloksia verrattiin mahdollisuuksien mukaan analyyttisin menetelmin tehtyihin vertailulaskelmiin. Työn tarkoituksena oli selvittää tuottivatko eri ohjelmat erilaisia tuloksia samoista kuormitustapauksista ja kuinka paljon tulokset erosivat.

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In this Thesis, we study various aspects of ring dark solitons (RDSs) in quasi-two-dimensional toroidally trapped Bose-Einstein condensates, focussing on atomic realisations thereof. Unlike the well-known planar dark solitons, exact analytic expressions for RDSs are not known. We address this problem by presenting exact localized soliton-like solutions to the radial Gross-Pitaevskii equation. To date, RDSs have not been experimentally observed in cold atomic gases, either. To this end, we propose two protocols for their creation in experiments. It is also currently well known that in dimensions higher than one, (ring) dark solitons are susceptible, in general, to an irreversible decay into vortex-antivortex pairs through the snake instability. We show that the snake instability is caused by an unbalanced quantum pressure across the soliton's notch, linking the instability to the Bogoliubov-de Gennes spectrum. In particular, if the angular symmetry is maintained (or the toroidal trapping is restrictive enough), we show that the RDS is stable (long-lived with a lifetime of order seconds) in two dimensions. Furthermore, when the decay does take place, we show that the snake instability can in fact be reversible, and predict a previously unknown revival phenomenon for the original (many-)RDS system: the soliton structure is recovered and all the point-phase singularities (i.e. vortices) disappear. Eventually, however, the decay leads to an example of quantum turbulence; a quantum example of the laminar-to-turbulent type of transition.

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Espinhaço and Mantiqueira are two mountain ranges of great importance in Brazil. In the uppermost parts of these areas, unique ecosystems occur, generally associated with rock outcrops, they are collectively called High Altitude Rocky Complexes. These environments show distinct soil and biota characteristics in relation to the surrounding biome. The soils are generally shallow, coarse textured, with high Al3+ and varying amounts of organic matter. Entisols, Inceptsols and Histosols are dominant, directly associated with the rock outcrops, and forming a complex mosaic of soils. Some of these soils are endemic, based on peculiar conditions of parent materials, topography and vegetation, and this pedodiversity is important for detecting unique and endangered soils. In these soils, organic matter is highly humified, with a great amount of soluble forms and conspicuous presence of charcoal. Spodic horizons and dark water rivers are typically associated with quartzite and quartzite outcrops, formed by illuviation of organic compounds, being less common in granitic rocks. The very low nutrient content of these soils and other environmental limitations required the development of specific physiological and morphological plant adaptations. Most high altitude environments are unstable under current climatic conditions, and anthropic interventions may be accelerating this process. Detailed soil surveys are necessary for a better understanding of the role of these soils in ecological processes and for the development of adequate conservation policies.

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The effects of the benzodiazepine1 (BZ1) receptor agonist SX-3228 were studied in rats (N = 12) implanted for chronic sleep procedures. Administration of 0.5, 1.0 and 2.5 mg/kg SX-3228, sc, to rats 1 h after the beginning of the light phase of the light-dark cycle induced a significant reduction of rapid-eye-movement sleep (REMS) during the third recording hour. Moreover, slow wave sleep (SWS) was increased during the fourth recording hour after the two largest doses of the compound. Administration of 0.5, 1.0 and 2.5 mg/kg SX-3228 one hour after the beginning of the dark period of the light-dark cycle caused a significant and maintained (6-h recording period) reduction of waking (W), whereas SWS and light sleep (LS) were increased. REMS values tended to increase during the entire recording period; however, the increase was statistically significant only for the 1.0 mg/kg dose during the first recording hour. In addition, a significant and dose-related increase of power density in the delta and the theta regions was found during nonREM sleep (LS and SWS) in the dark period. Our results indicate that SX-3228 is a potent hypnotic when given to the rat during the dark period of the light-dark cycle. Moreover, the sleep induced by SX-3228 during the dark phase closely resembles the physiological sleep of the rat.

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The dorsal periaqueductal gray (DPAG) has been implicated in the behavioral and autonomic expression of defensive reactions. Several results suggest that, along with GABA, glutamate and serotonin, nitric oxide (NO) may play a role in defense reactions mediated by this region. To further investigate this possibility we microinjected methylene blue (MB; 10, 30 or 100 nmol/0.5 µl) into the DPAG of rats submitted to the elevated plus-maze test, an animal model of anxiety. MB has been used as an inhibitor of soluble guanylate cyclase (sGC) to demonstrate cGMP-mediated processes, and there is evidence that NO may exert its biological effects by binding to the heme part of guanylate cyclase, causing an increase in cGMP levels. The results showed that MB (30 nmol) significantly increased the percent of time spent in the open arms (saline = 11.57 ± 1.54, MB = 18.5 ± 2.45, P<0.05) and tended to do the same with the percentage of open arm entries (saline = 25.8 ± 1.97, MB = 33.77 ± 3.07, P<0.10), but did not change the number of enclosed arm entries. The dose-response curve, however, had an inverted U shape. These results indicate that MB, within a limited dose range, has anxiolytic properties when microinjected into the DPAG.

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The zebrafish (Danio rerio) has been used as a model in neuroscience but knowledge about its behavior is limited. The aim of this study was to determine the preference of this fish species for a dark or light environment. Initially we used a place preference test and in a second experiment we applied an exit latency test. A two-chamber aquarium was used for the preference test. The aquarium consisted of a black chamber and a white chamber. In the first experiment the animal was placed in the aquarium and the time spent in the two compartments was recorded for 10 min. More time was spent in the black compartment (Wilcoxon matched-pairs signed-rank test, T = 7, N1 = N2 = 18, P = 0.0001). In the second experiment the animal was placed in the black or white compartment and the time it took to go from the initial compartment to the opposite one was recorded. The test lasted a maximum of 10 min. The results showed that the animal spent more time to go from the black to the white compartment (Mann-Whitney rank sum test, T = 48, N1 = 9, N2 = 8, P<0.0230). These data suggest that this fish species has a natural preference for a dark environment and this characteristic can be very useful for the development of new behavioral paradigms for fish.