The evolution of protoplanetary disks is believed to be driven largely by angular momentum transport resulting from magnetized disk winds and turbulent viscosity. The ionization of the disk that is essential for these processes has been thought to be due to host star coronal X-rays but could also arise from energetic particles produced by coronal flares, or traveling shock waves, and advected by the stellar wind. We have performed test-particle numerical simulations of energetic protons propagating into a realistic T. Tauri stellar wind, including a superposed small-scale magnetostatic turbulence. The isotropic (Kolmogorov power spectrum) turbulent component is synthesized along the individual particle trajectories. We have investigated the energy range [0.1-10] GeV, consistent with expectations from Chandra X-ray observations of large flares on T. Tauri stars and recent indications by the Herschel Space Observatory of a significant contribution of energetic particles to the disk ionization of young stars. In contrast with a previous theoretical study finding a dominance of energetic particles over X-rays in the ionization throughout the disk, we find that the disk ionization is likely dominated by X-rays over much of its area, except within narrow regions where particles are channeled onto the disk by the strongly tangled and turbulent magnetic field. The radial thickness of such regions is 5 stellar radii close to the star and broadens with increasing radial distance. This likely continues out to large distances from the star (10 au or greater), where particles can be copiously advected and diffused by the turbulent wind.

High-resolution spectroscopic observations were taken of 29 extended main-sequence turnoff (eMSTO) stars in the young (similar to 200 Myr) Large Magellanic Cloud (LMC) cluster, NGC 1866, using the Michigan/Magellan Fiber System and MSpec spectrograph on the Magellan-Clay 6.5 m telescope. These spectra reveal the first direct detection of rapidly rotating stars whose presence has only been inferred from photometric studies. The eMSTO stars exhibit Ha emission (indicative of Be-star decretion disks), others have shallow broad H alpha absorption (consistent with rotation. greater than or similar to 150 km s(-1)), or deep Ha core absorption signaling lower rotation velocities (less than or similar to 150 km s(-1)). The spectra appear consistent with two populations of stars-one rapidly rotating, and the other, younger and slowly rotating.

Aims. The aim of this work is to constrain properties of the disk around the archetype FU Orionis object, FU Ori, with as good as similar to 25 au resolution. Methods. We resolved FU Ori at 29-37 GHz using the Karl G. Jansky Very Large Array (JVLA) in the A-array configuration, which provided the highest possible angular resolution to date at this frequency band (similar to 0 ''.07). We also performed complementary JVLA 8-10 GHz observations, Submillimeter Array (SMA) 224 GHz and 272 GHz observations, and compared these with archival Atacama Large Millimeter Array (ALMA) 346 GHz observations to obtain the spectral energy distributions (SEDs). Results. Our 8-10 GHz observations do not find evidence for the presence of thermal radio jets, and constrain the radio jet/wind flux to at least 90 times lower than the expected value from the previously reported bolometric luminosity-radio luminosity correlation. The emission at frequencies higher than 29 GHz may be dominated by the two spatially unresolved sources, which are located immediately around FU Ori and its companion FU Ori S, respectively. Their deconvolved radii at 33 GHz are only a few au, which is two orders of magnitude smaller in linear scale than the gaseous disk revealed by the previous Subaru-HiCIAO 1.6 mu m coronagraphic polarization imaging observations. We are struck by the fact that these two spatially compact sources contribute to over 50% of the observed fluxes at 224 GHz, 272 GHz, and 346 GHz. The 8-346 GHz SEDs of FU Ori and FU Ori S cannot be fit by constant spectral indices (over frequency), although we cannot rule out that it is due to the time variability of their (sub)millimeter fluxes. Conclusions. The more sophisticated models for SEDs considering the details of the observed spectral indices in the millimeter bands suggest that the >29 GHz emission is contributed by a combination of free-free emission from ionized gas and thermal emission from optically thick and optically thin dust components. We hypothesize that dust in the innermost parts of the disks (less than or similar to 0.1 au) has been sublimated, and thus the disks are no longer well shielded against the ionizing photons. The estimated overall gas and dust mass based on SED modeling, can be as high as a fraction of a solar mass, which is adequate for developing disk gravitational instability. Our present explanation for the observational data is that the massive inflow of gas and dust due to disk gravitational instability or interaction with a companion/intruder, was piled up at the few-au scale due to the development of a deadzone with negligible ionization. The piled up material subsequently triggered the thermal instability and the magnetorotational instability when the ionization fraction in the inner sub-au scale region exceeded a threshold value, leading to the high protostellar accretion rate.

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Thesis advisor: Jeremy D. Shakun / Glaciers in the tropics have undergone significant retreat in the past several decades, but the magnitude of this retreat in the long-term context of the Holocene has mostly been qualitatively assessed. This study produces a quantitative reconstruction of Holocene glacier extent relative to today from the Quelccaya Ice Cap, Peru, and the Rwenzori Mountains of east Africa. I use measurements of in situ 14C and 10Be from bedrock that was recently exposed by glacier retreat to constrain possible bedrock exposure and erosion histories at each site. The results are strikingly similar in both areas, and suggest that ice was generally smaller than today during the first half of the Holocene and larger than today for most, if not all, of the last several millennia. These findings give evidence toward a coherent Holocene expansion of glaciers across the tropics, and suggest that recent retreat is unusual in a multi-millennial context. / Thesis (MS) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Syftet med studien var att undersöka hur fritidspedagoger arbetar med utomhusaktiviteter och vilka möjligheter och svårigheter som ofta framkommer i fritidspedagogernas beskrivningar av att arbeta i en utomhusmiljö. För att komma fram till studiens syfte utförde vi tio kvalitativa intervjuer med fritidslärare och förskolelärare på olika skolor. Materialet som vi samlade in analyserades utifrån en tematisk analys och för att bättre förstå analysdelen har vi delat in den i följande tre teman: Lärarens roll i en utomhusmiljö, Fritidslärarens undervisning utomhus och till sist Miljöns betydelse för elevernas lärande. Resultatet av studien visar hur fritidshemsläraren har två olika roller i utomhusmiljön där den ena var att övervaka verksamheten och den andra handlade om att genomföra styrda och planlagda utomhusaktiviteter som resulterade i att stimulera elevernas sociala relationer, kommunikation och gemenskap. Förutom det här resultatet har vår undersökning påvisat att det finns svårigheter och utmaningar med att utföra utomhusaktiviteter på grund av t.ex. resursbrister, välutbildad personal, elever som har sociala svårigheter samt olika miljöbrister.

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Syftet med detta examensarbete är att genom en kvalitativ undersökningsmetod ta reda på hur lärare lär ut naturorienterande begrepp till sina elever. Arbetets mål är att få en bild av NO-lärares perspektiv på sin undervisning i förhållande till forskning. För att ta reda på relevant information inom detta område genomfördes en kvalitativ undersökning där lärare intervjuades om deras undervisning bl. a av begreppen fotosyntes och friktion. Resultatet utgår från empiri anknutit till utförda lärarintervjuer för att ge läsaren förståelse och kunskap om olika problem som kan uppstå vid undervisning av naturorienterande begrepp. En tydlig svårighet som alla de deltagande lärarna upplyste om, är att få eleverna att förstå innebörden av ett begrepp och sedan att få dem att använda sig av ett mer naturvetenskapligt språkbruk. Alla de deltagande lärarna anser att de svårigheter som elever har inom de naturorienterande ämnena beror främst på grund av att det naturvetenskapliga språket skiljer sig enormt från elevernas vardagliga språkbruk. Det gör att ämnesspråket som används i naturorienterad undervisning kan uppfattats vara komplext och främmande. Det är lärarens ansvar att lära ut alla dessa abstrakta begrepp genom att göra dem gripbara och kända för eleverna. Det är många elever som har svårt att beskriva och förstå ämnesinnehållet i biologi, fysik och kemi, vilket kan sammankopplas till att en stor andel elever inte når upp till ämnenas kunskapskrav. En stor orsak till detta är på grund av att undervisningen inte anses vara tillräcklig konkret i att lära ut begrepp. Materialet från intervjuerna analyseras utifrån det teoretiska perspektivet - Pedagogical Content Knowledge som kommer här efter förkortas till PCK. Vår analys utgår från PCK för att undersöka och analysera lärarens ämneskunskaper och pedagogiska kunskaper utifrån deras erfarenhet inom läraryrket. Resultatet från studien visar att de deltagande lärarna försöker att ge eleverna förståelse om olika begrepp såsom fotosyntes och friktion genom att använda sig av ett korrekt naturvetenskapligt språk när de undervisar. Lärarna beskriver att deras elever behöver arbeta flitigt med naturorienterande begrepp i olika sammanhang för att kunna lägga till begreppen i sitt ordförråd och att de har som lärare en ledande roll i elevernas lärande. Utifrån deras resonemang diskutera denna studie om lärarnas val av strategier för att lära ut begrepp i undervisningssammanhang och vilken komplexitet det innebär för läraren.

In response to Irish philosopher Richard Kearney’s recent proposal of a post-metaphysical re-imagination of God, the thesis asks how we may begin to reimagine the Christ-event, post-metaphysically. Specifically, it investigates the implications of such post-metaphysical thought for the theological categories of hamartiology and soteriology. Methodologically, the thesis proceeds from hermeneutical re-readings of biblical narratives and traditions. Via an archaeology of the biblical yetser, the concept of imagination is offered as a way to re-imagine sin and salvation. The Eden narrative is read within its ancient Near Eastern context, and the narratives of the Annunciation and Transfiguration also receives special mention, as well as the window that Song of Songs opens on the metaphor of the desire of God. What results from this approach is, first, yet another deconstruction of the Augustinian formulation of original sin, as well as an eschatological reinterpretation of the Christ event in terms of the messianic Kingdom of God. Christ, who submits his yetser to the will of the Father in an act of worshipful surrender, becomes the perfect embodiment of the Word of God to a humanity whose yetser is perpetually put in service of itself in an act of idolatry. The enabling of the Kingdom of God in Jesus, who embodies the human telos, captures the human imagination and transfigures humanity through the existential experience of transcendence which breaks into its concrete reality through the Christ-event and its retelling. In this way, realised eschatology is possibilised through the imagination. Christ as prototype of the divinely intended telos of humanity becomes an existential possibility via the transfiguration, enacted by the imagination. This enables humanity to become co-creators with God of a new creation, symbolised by God’s messianic Kingdom of love and justice. / Thesis (PhD)--University of Pretoria, 2016. / University of Pretoria Postgraduate bursary / Dogmatics and Christian Ethics / PhD / Unrestricted