9,341 research outputs found
A quasi-time-dependent radiative transfer model of OH104.9+2.4
We investigate the pulsation-phase dependent properties of the circumstellar
dust shell (CDS) of the OH/IR star OH104.9+2.4 based on radiative transfer
modeling (RTM) using the code DUSTY. Our previous study concerning simultaneous
modeling of the spectral energy distribution (SED) and near-infrared (NIR)
visibilities (Riechers et al. 2004) has now been extended by means of a more
detailed analysis of the pulsation-phase dependence of the model parameters of
OH104.9+2.4. In order to investigate the temporal variation in the spatial
structure of the CDS, additional NIR speckle interferometric observations in
the K' band were carried out with the 6 m telescope of the Special
Astrophysical Observatory (SAO). At a wavelength of 2.12 micron the
diffraction-limited resolution of 74 mas was attained. Several key parameters
of our previous best-fitting model had to be adjusted in order to be consistent
with the newly extended amount of observational data. It was found that a
simple rescaling of the bolometric flux F_bol is not sufficient to take the
variability of the source into account, as the change in optical depth over a
full pulsation cycle is rather high. On the other hand, the impact of a change
in effective temperature T_eff on SED and visibility is rather small. However,
observations, as well as models for other AGB stars, show the necessity of
including a variation of T_eff with pulsation phase in the radiative transfer
models. Therefore, our new best-fitting model accounts for these changes.Comment: 7 pages, including 5 postscript figures and 3 tables. Published in
Astronomy and Astrophysics. (v1: accepted version; v2: published version,
minor grammatical changes
The relationship between individual differences in rumination, distractibility, and depression
According to the response styles theory, rumination and distraction are two different ways to respond to a negative stimulus. Previous studies on the relationship between rumination and distraction and their effect on depression have focused mainly on the active use of these response styles. In the present study, we examined how the natural tendency to be distractible was related to rumination or depression. Participants were asked to answer questionnaires to rumination, distractibility, and depression, and to perform an attention task. Self-reported level of rumination, depression, and distractibility all had a positive correlation with each other. However, task performance indexed by accuracy had a negative correlation with rumination. Contrary to our predictions, the results suggested that higher depression is related to more negative self-evaluation of distractibility. However, objective evidence of distractibility was related to less rumination, which was consistent with our predictions
Fracture toughness and crack-resistance curve behavior in metallic glass-matrix composites
Nonlinear-elastic fracture mechanics methods are used to assess the fracture toughness of bulk metallic glass (BMG) composites; results are compared with similar measurements for other monolithic and composite BMG alloys. Mechanistically, plastic shielding gives rise to characteristic resistance-curve behavior where the fracture resistance increases with crack extension. Specifically, confinement of damage by second-phase dendrites is shown to result in enhancement of the toughness by nearly an order of magnitude relative to unreinforced glass
Fabrication of elastomeric stamps with polymer-reinforced sidewalls via chemically selective vapor deposition polymerization of poly(p-xylylene)
We report on the preparation of polydimethylsiloxane stamps with selectively grown polymer sidewalls by chemical vapor deposition polymerization of poly(ppoly(p-xylylene). Using a thin iron layer as an inhibitor, the deposition occurs only on the sidewalls of the features in relief, resulting in a polymer-reinforced stamp. The wetting properties of stamps can be restored after removing the thin iron layer with an acidic solution, which has been verified by pattern transfer to an underlying substrate using molding and microcontact printing. © 2003 American Institute of Physics.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/69846/2/APPLAB-83-20-4250-1.pd
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