Narrative Companionship: Philosophy, Gender Stereotypes, and Young Adult Literature

Zuidervaart, L. [Promotor]Musschenga, A.W. [Promotor

Circumstellar interaction in supernovae in dense environments - an observational perspective

In a supernova explosion, the ejecta interacting with the surrounding circumstellar medium (CSM) give rise to variety of radiation. Since CSM is created from the mass lost from the progenitor star, it carries footprints of the late time evolution of the star. This is one of the unique ways to get a handle on the nature of the progenitor star system. Here, I will focus mainly on the supernovae (SNe) exploding in dense environments, a.k.a. Type IIn SNe. Radio and X-ray emission from this class of SNe have revealed important modifications in their radiation properties, due to the presence of high density CSM. Forward shock dominance of the X-ray emission, internal free-free absorption of the radio emission, episodic or non-steady mass loss rate, asymmetry in the explosion seem to be common properties of this class of SNe.Comment: Fixed minor typos. 31 pages, 9 figures, accepted for publication in Space Science Reviews. Chapter in International Space Science Institute (ISSI) Book on "Supernovae" to be published in Space Science Reviews by Springe

Origin and evolution of the light nuclides

After a short historical (and highly subjective) introduction to the field, I discuss our current understanding of the origin and evolution of the light nuclides D, He-3, He-4, Li-6, Li-7, Be-9, B-10 and B-11. Despite considerable observational and theoretical progress, important uncertainties still persist for each and every one of those nuclides. The present-day abundance of D in the local interstellar medium is currently uncertain, making it difficult to infer the recent chemical evolution of the solar neighborhood. To account for the observed quasi-constancy of He-3 abundance from the Big Bang to our days, the stellar production of that nuclide must be negligible; however, the scarce observations of its abundance in planetary nebulae seem to contradict this idea. The observed Be and B evolution as primaries suggests that the source composition of cosmic rays has remained quasi-constant since the early days of the Galaxy, a suggestion with far reaching implications for the origin of cosmic rays; however, the main idea proposed to account for that constancy, namely that superbubbles are at the source of cosmic rays, encounters some serious difficulties. The best explanation for the mismatch between primordial Li and the observed "Spite-plateau" in halo stars appears to be depletion of Li in stellar envelopes, by some yet poorly understood mechanism. But this explanation impacts on the level of the recently discovered early ``Li-6 plateau'', which (if confirmed), seriously challenges current ideas of cosmic ray nucleosynthesis.Comment: 18 pages, 9 figs. Invited Review in "Symposium on the Composition of Matter", honoring Johannes Geiss on the occasion of his 80th birthday (Grindelwald, Switzerland, Sept. 2006), to be published in Space Science Series of ISS

Enhanced sensitivity and responses to viologens from a whole-cell bacterial bioreporter treated with branched polyethyleneimines

Aims: Evaluate the use of polyethyleneimines (PEIs) as membrane permeabilizers to improve the responses and sensitivity of a bacterial bioreporter strain to viologens. Methods and Results: The responses from E. coli str. EBS, i.e., E. coli BW25113 carrying plasmid pSDS, when exposed to five different viologens were characterized, as were the toxicities of seven different PEIS, including two linear and five branched species. Based on these results, benzyl viologen led to the greatest responses, and 0??8-kDa branched PEI (BPEI) was the least toxic of the PEIs tested and, therefore, both were selected for the subsequent tests. The bioluminescence and relative responses from E. coli str. EBS exposed to various concentrations of 0??8 kDa BPEI identified 400 mg l−1 as the optimal concentration. Using this concentration, tests were performed with all five of the viologens. Conclusions: The responses from E. coli str. EBS to the viologens were improved, with the maximum relative bioluminescence values increasing between 5??6 and 16??5-fold. The minimum detectable levels for four of the viologens were likewise improved 2- to 4-fold. Significance and Impact of Study: Improving bacterial membrane permeability in a controlled manner using BPEIs can improve biosensing of toxic compounds, as well as be used in biofuel and bioenergy applications where membrane permeability to a solute is important