IR Kuiper Belt Constraints

We compute the temperature and IR signal of particles of radius $a$ and albedo $\alpha$ at heliocentric distance $R$, taking into account the emissivity effect, and give an interpolating formula for the result. We compare with analyses of COBE DIRBE data by others (including recent detection of the cosmic IR background) for various values of heliocentric distance, $R$, particle radius, $a$, and particle albedo, $\alpha$. We then apply these results to a recently-developed picture of the Kuiper belt as a two-sector disk with a nearby, low-density sector (40<R<50-90 AU) and a more distant sector with a higher density. We consider the case in which passage through a molecular cloud essentially cleans the Solar System of dust. We apply a simple model of dust production by comet collisions and removal by the Poynting-Robertson effect to find limits on total and dust masses in the near and far sectors as a function of time since such a passage. Finally we compare Kuiper belt IR spectra for various parameter values.Comment: 34 pages, LaTeX, uses aasms4.sty, 11 PostScript figures not embedded. A number of substantive comments by a particularly thoughtful referee have been addresse

A step towards commercial adaptive hypermedia

As is well known in the Adaptive Hypermedia (AH) community, AH systems (AHS) have a tendency to be academic systems only, mainly used as personalized learning tools. There is, however, a strong desire in AH to extend beyond the world of education and research, and move towards the "real" world, i.e., the commercial world. We are here presenting such an expansion, in the form of an extension of an existing commercial authoring tool for WYSIWYG (Web-)content, Content-e, with AH capability. The extended product is called Content-e/LAOS, as it is based on the LAOS framework for authoring of adaptive hypermedia. The paper presents Content-e/LAOS, one of the first commercial AHS, as well as some evaluation results

A Step towards Commercial Adaptive Hypermedia

Abstract. As is well known in the Adaptive Hypermedia (AH) community, AH systems (AHS) have a tendency to be academic systems only, mainly used as personalized learning tools. There is, however, a strong desire in AH to extend beyond the world of education and research, and move towards the “real” world, i.e., the commercial world. We are here presenting such an expansion, in the form of an extension of an existing commercial authoring tool for WYSIWYG (Web-)content, Content-e, with AH capability. The extended product is called Content-e/LAOS, as it is based on the LAOS framework for authoring of adaptive hypermedia. The paper presents Content-e/LAOS, one of the first commercial AHS, as well as some evaluation results.

Mitochondrial PE potentiates respiratory enzymes to amplify skeletal muscle aerobic capacity

Exercise capacity is a strong predictor of all-cause mortality. Skeletal muscle mitochondrial respiratory capacity, its biggest contributor, adapts robustly to changes in energy demands induced by contractile activity. While transcriptional regulation of mitochondrial enzymes has been extensively studied, there is limited information on how mitochondrial membrane lipids are regulated. Here, we show that exercise training or muscle disuse alters mitochondrial membrane phospholipids including phosphatidylethanolamine (PE). Addition of PE promoted, whereas removal of PE diminished, mitochondrial respiratory capacity. Unexpectedly, skeletal muscle–specific inhibition of mitochondria-autonomous synthesis of PE caused respiratory failure because of metabolic insults in the diaphragm muscle. While mitochondrial PE deficiency coincided with increased oxidative stress, neutralization of the latter did not rescue lethality. These findings highlight the previously underappreciated role of mitochondrial membrane phospholipids in dynamically controlling skeletal muscle energetics and function