Redshift estimate of a gravitational lens from the observed reddening of a multiply imaged quasar

Light rays from a multiply imaged quasar usually sample different path lengths across the deflector. Extinction in the lensing galaxy may thus lead to a differential obscuration and reddening between the observed macro-lensed QSO images. These effects naturally depend on the precise shape of the extinction law and on the redshift of the lens. By means of numerical Monte-Carlo simulations, using a least-squares fitting method and assuming an extinction law similar to that observed in the Galaxy, we show how accurate photometric observations of multiply imaged quasars obtained in several spectral bands could lead to the estimate of the lens redshift, irrespective of the visibility of the deflector. Observational requirements necessary to apply this method to real cases are thoroughly discussed. If extinction laws turn out to be too different from galaxy to galaxy, we find out that more promising observations should consist in getting high signal-to-noise low resolution spectra of at least three distinct images of a lensed quasar, over a spectral range as wide as possible, from which it should be straightforward to extract the precise shape of the redshifted extinction law. Very high signal-to-noise, low spectral resolution, VLT observations of H1413+117 and MG 0414+0534 should enable one to derive such a redshifted extinction law.Comment: 7 pages, 11 figures, to appear in Astronomy and Astrophysics (also available at http://vela.astro.ulg.ac.be/preprint/

The Birth of a Super Star Cluster: NGC 5253

We present images of the 7mm free-free emission from the radio "supernebula" in NGC 5253 made with the Very Large Array and the Pie Town link. The images reveal structure in the nebula, which has a <~ 1 pc (~50 mas radius) core requiring the excitation of 1200 O7 stars. The nebula is elongated, with an arc of emission curving to the northeast and to the south. The total ionizing flux within the central 1.2" (~20 pc) is 7 x 10^52 s^-1, corresponding to 7000 O7 stars. We propose that the radio source is coincident with a small, very red near-infrared cluster and apparently linked to a larger, optical source some 10 pc away on the sky. We speculate on the causes of this structure and what it might tell us about the birth of the embedded young super star cluster.Comment: Accepted, Astrophysical Journal Letters. 10 pages, including 2 figure

Natural Resource Abundance and Human Capital Accumulation

This study examines indicators of human capital accumulation together with data for natural resource abundance and rents in a panel of 102 countries running from 1970 to 1999. Mineral wealth makes a positive and marked difference on human capital accumulation. Matching on observables reveals that cross-country results are not driven by a third factor such as overall economic development. Political stability does seem to affect both human capital accumulation and subsoil wealth, but not enough to overturn my conclusions. Instrumentation reveals that reverse causality running from education to natural resources does not drive the results. Estimation of a panel VAR indicates that, over the three decades, a $1 shock to resource rent generates five cents of extra educational expenditure per year. These results are consistent with Hirschman's conjecture that enclave economies have weaker production leakages but stronger government revenue linkages than other activities. The "wealth channel" identified in this paper implies that caution should be exerted when discouraging countries from exploiting their mineral wealth, especially for countries where human capital is scarce.Labor and Human Capital, Resource /Energy Economics and Policy,

Enhancement of Opioid-Mediated Analgesia\ud by Ingestion of Amniotic Fluid:\ud Onset Latency and Duration

Ingestion of placenta and amniotic fluid has been shown to enhance opioid-mediated analgesia produced by morphine injection, footshock, vaginal/cervical stimulation, and during late pregnancy in rats. The present study was designed to determine how soon after ingestion the enhancement begins and how long it lasts. Tail-flick latencies in Long-Evans rats were determined before and during vaginal/cervical stimulation; analgesia was measured as the percent increase in tail-flick latency during vaginal stimulation. After determination of baseline, rats were intubated with 0.25 ml of either amniotic fluid or beef bouillon. We found that analgesia enhancement was detectable as early as 5 minutes after ingestion of amniotic fluid, and the effect lasted at least 30 minutes, but no longer than 40 minutes

Effect of adsorbed water on the specific surface area of some standards cotton

It is well known that cotton fibers are sensitive to moisture. The interactions of cellulose chains and water molecules could therefore have an influence on the fiber properties. In this presentation, we will investigate the effect of adsorbed water on the specific surface area of standards cotton fibers. The amount of adsorbed water was determined by Thermogravimetric analysis. Adsorption of methylene blue in aqueous phase was used to measure the surface specific area. A numerical relationship of the form SBM =a +b X has been obtained, where SBM represents the specific surface area, X the percentage of adsorbed water, a and b are experimental constants. (Résumé d'auteur