363 research outputs found
Dust formation in astrophysical environments: the importance of kinetics
Laboratory astrophysics and astrochemistr
Stability of polycyclic aromatic hydrocarbon clusters in protoplanetary discs
Interstellar matter and star formatio
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Modeling the infrared cascade spectra of small PAHs: the 11.2 mu m band
The profile of the 11.2 μm feature of the infrared (IR) cascade emission spectra of polycyclic aromatic hydrocarbon (PAH) molecules is investigated using a vibrational anharmonic method. Several factors are found to affect the profile including: the energy of the initially absorbed ultraviolet (UV) photon, the density of vibrational states, the anharmonic nature of the vibrational modes, the relative intensities of the vibrational modes, the rotational temperature of the molecule, and blending with nearby features. Each of these factors is explored independently and influence either the red or blue wing of the 11.2 μm feature. The majority impact solely the red wing, with the only factor altering the blue wing being the rotational temperature
Mid-infrared spectroscopic signatures of dibenzopyrene cations: the effect of symmetry on PAH IR spectroscopy
Interstellar matter and star formatio
Hydrogenation and dehydrogenation of interstellar PAHs: Spectral characteristics and H_2 formation
Interstellar matter and star formationLaboratory astrophysics and astrochemistr
Mechanisms of attention for cues associated with rewarding and aversive outcomes
Attentional biases arising from classical conditioning processes may contribute to the maintenance of drug addictions and anxiety disorders. This thesis examined whether attentional mechanisms for conditioned stimuli (CS) would be dominated by affective properties (Lang, Greenwald, Bradley, & Hamm, 1993), or the uncertainty of the stimulus in predicting the outcome (Pearce & Hall, 1980). In chapter one affective and uncertainty-driven mechanisms of attention are discussed in relation to rewarding and aversive outcomes. In experimental chapter 2 methodological issues are addressed. In experimental
chapters three and four attentional mechanisms are tested using a discriminative conditioning procedure with visual stimuli of varying predictive certainty (CS+,CS+/-,CS-)
for a monetary or noise outcome (US). Attention was measured using an eye-tracker, and emotional conditioning and learning were measured using Likert scales. It was found that attention was mediated by uncertainty (chapter 3), but increasing the intensity of the outcome switched attention to affective-driven mechanisms for the noise outcome (chapter 4). In a further experiment this effect on attention remained for the noise outcome even
under conditions promoting uncertainty-driven mechanisms (chapter 6). When cigarettes were the unconditioned stimuli instead of money in the appetitive conditioning, attention was also mediated by stimulus affect (chapter 5). In chapter 7 the data are discussed and it is concluded that when the outcome is highly emotionally salient, affective-driven mechanisms of attention dominate over uncertainty
Polycyclic Aromatic Hydrocarbon emission model in photodissociation regions - I.: Application to the 3.3, 6.2, and 11.2 μm bands
Laboratory astrophysics and astrochemistryInterstellar matter and star formatio
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