>Magister Scientiae - MSc / The study of neutral atomic hydrogen (HI) plays a vital role in improving the knowledge about galaxy evolution since HI serves as the raw fuel for star formation. However, the current knowledge about it is limited to the nearby Universe due to its intrinsic faintness and the inadequate sensitivities of the current radio telescopes.

The purpose of this study was to observe and analyze the factors that lead to a child's increase in responding to a previously neutral stimulus after observing another child's behavior and consequences in the same setting. The effects of five video presentations on rate of button-pressing responses were observed across four students. Rates of button-pressing behavior on an FR3 schedule of reinforcement were collected for each student using a computer and a metal apparatus with two flat push buttons. Each student completed two baseline phases to establish neutrality of stimuli, and viewed a total of five video presentations. Each video segment contained a model engaging in button pressing and receiving tokens under various social and nonsocial conditions, which would potentially serve as reinforcers. Rates of responding were recorded immediately after each video presentation. Three of the four students' rates of responding increased and surpassed their levels of responding during baseline sessions. From these results, it was concluded that neutral stimuli can acquire reinforcing properties for children through an observational learning procedure. It is suggested that observational learning (the presentation of a model engaging in a specific behavior) might be considered and establishing operation to temporarily increase the value of a reinforcer.

Cette recherche se focalise sur la posture Neutre face au Chaos. Elle émerge d’une volonté de rompre avec une lecture paradigmatique de l’urbanisation et d’un désir de trouver un rapport apaisé avec le Chaos urbain qui nous entoure, un Chaos qui n’est plus la congestion spectaculaire de la Grande Ville mais un Chaos gris : diffus, silencieux, insignifiant. Ce regard que l’on qualifierait de Neutre est proche d’une certaine quiétude de l’esprit que l’on trouve dans le Zen ou le Taoïsme. Comme dans ces philosophies orientales il exprime une déconnexion et un dé-saisissement.Le Neutre est une expérience immédiate du réel qui implique une destitution du sujet, la sortie du rapport duel sujet-objet pour tenter une expérience indistincte de l’événement, sur un mode fusionnel, de réceptivité totale. Mais le Neutre qui nous intéresse dans cette recherche est un Neutre créatif et non pas purement contemplatif, un Neutre susceptible de ‘faire projet’. Ce Neutre, en tant que récepteur du Chaos, cherche à transformer la vitalité chaotique en processus actif. Notre argument principal se porte sur ce potentiel créatif et productif de la posture Neutre, et de sa manière à se saisir du Chaos comme source intarissable.La recherche s’organise selon des principes de fragmentation, transdisciplinarité, assemblage et redondance. Les onze figures qui la composent sont autonomes mais elles ne sont pas de la même nature. En effet, elles s’organisent en trois chapitres distincts, qui correspondent aux trois temps, ou trois mécanismes de la posture Neutre : (1) l’indiscernabilité (ou le Neutre réceptif), (2) le Désengagement (ou le Neutre passif) et (3) l’Énonciation (le Neutre actif). Ainsi, les trois premières figures (le Bruit, le Conflit et le Noeud), qui composent le premier chapitre, se rapportent à la réalité exogène, à ce qui se situe en dehors de nous et qui nous entoure ; les cinq figures qui suivent (l’Indifférence, le Laissez-faire, l’Idiotie, la Retraite et l’Infirmité) se rapportent toutes à l’attitude du sujet lui-même, à sa posture passive vis-à-vis du monde ; alors que les trois dernières figures (le Gris, le Pathos et l’Acceptation Active) se rapportent aux moyens d’expression et à l’accès au langage, c’est-à-dire à l’énonciation du projet.La recherche révèle que la posture Neutre ne constitue pas une méthode mais une démarche. Certes, une démarche n’a pas la même force transformatrice qu’une méthode. Elle est plus difficile à partager et à décrire. Elle est impossible à appliquer de façon constante et continue. Cependant, elle peut s’avérer tout aussi précieuse en tant que pensée du projet. / This research focuses on a Neutral posture towards Chaos. It comes from the will to break with a paradigmatic reading of urbanisation and from a desire to find a pacified relationship with the urban Chaos surrounding us, a Chaos which is no longer the spectacular congestion of the Großstadt, but a grey Chaos : diffuse, silent, insignificant. This view, that we qualify as Neutral is close to a certain quietude of the mind that might be found in Zen or Taoism. Like in these eastern philosophies, it expresses a form of disconnection and divestiture. The Neutral is an immediate experience of the real which implies a destitution of the subject, an exit from the dual relationship of subject-object to attempt an indistinctive experience of the event, in a fusional mode, of total receptiveness. But the Neutral on which we are focused in this research is a creative Neutral and not a purely contemplative one, a Neutral which is likely to become a means of projection. This Neutral as a receptor of Chaos, tries to transform chaotic vitality into an active process. Our main argument focuses on this creative and productive potential of the Neutral posture and on its way of taking hold of Chaos as an inexhaustible source. The research is organised according to the principles of fragmentation, transdisciplinarity, assembly and redundancy. The eleven figures of which it is composed are autonomous and of various natures. Indeed, they are organised in three distinct chapters, which correspond to three different moments, or three mechanisms of the Neutral posture : (1) Indiscernibility  (or the receptive Neutral), (2) Disengagement (or the passive Neutral),(3) Enunciation (the active Neutral). Thus, the three figures (Noise, Conflict, Node)that make up the first chapter, relate to the exogenous reality, to that which is situated outside of us and that which surrounds us ; the five following figures (Indifference, Laissez-faire, Idiocy, Retreat and Infirmity) all relate to the attitude of the subject himself, to his passive posture towards the world ; whereas the three final figures (Grey, Pathos and Active Acceptance) relate to the ways of expression and to access to language, that is to say the enunciation of the project. The research reveals that the Neutral posture does not constitute a method but an approach. Certainly, an approach does not have the transformative force of a method. It is much more difficult to impart and to describe. It is impossible to apply in a way which is continuous and constant. However, it might turn out to be just as precious as a projective thought.

We report new studies on the early-time dynamics of ultracold neutral plasmas. We use fluorescence spectroscopy to probe plasma dynamics on the nanosecond time scale. We determine the rms ion velocity during the initial plasma period. The initial ion acceleration is found as the time derivative of the ion velocity. We compare to a theoretical model. The experimental results agree with the model at low plasma densities. However, the ion acceleration is a factor of ten lower than the model at higher densities. The cause of this discrepancy is currently unknown.

Interplanetary satellite missions and also satellites orbiting the Earth carry instruments to measure fluxes of neutral atoms, which are plasma key parameters for the investigation of the planets' atmospheres. Neutral atoms entering the mass-spectrometry instrument have to be ionized to be able to guide them using electric and magnetic fields with intent to determine energy and velocity of the atoms and finally their mass. For low energy neutral atoms, the ionization process can be realized by implementing a charge state conversion surface, where-on the atoms are scattered in an angle of grazing incidence and getting ionized.The objective of this work is the characterization and analysis of two diamond-like carbon surface samples by measuring and determining ionization efficiencies and scattering properties and therefore their functionality as charge state conversion surfaces.First, a chemical vapor deposition (CVD) diamond sample is investigated. Furthermore the CVD diamond is compared to another diamond--like carbon surface manufactured by pulsed laser deposition (PLD) technique. All measurements have been accomplished at the ILENA (Imager for Low Energy Neutral Atoms) facility at the Physics Institute, University of Bern in the Department of Space Research and Planetary Sciences.It is discovered that the CVD surface gets electrostatically charged upon scattering of atomic ions. Though this charging effects, a qualitative characterization of the surface can be made. It is shown that the ionization efficiencies of the CVD and the PLD diamond surface are of comparable quality, where on the contrary the scattering properties of the CVD diamond charge state conversion surface are much better. It still has to be investigated in future experiments, if this brilliant scattering properties are due to charging effects or can be assigned to the very smooth surface of the CVD diamond surface. / <p>Validerat; 20120112 (anonymous)</p>

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