Distribution of the Milliped \u3ci\u3eNarceus Americanus Annularis\u3c/i\u3e (Spirobolida: Spirobolidae) in Wisconsin

(excerpt) The spirobolid milliped Narceus americanus annularis Rafmesque 1820 is common and widespread throughout the eastern United States and Canada (Keeton 1960, Shelley 1988, Hoffman 1990). It has previously been recorded \ from Wisconsin. Cahn (1915) reported it from the Wingra Springs region in \ central Dane County, and Keeton (1960) reported it from Clark and Sauk Counties

From the Other Side: Women, Gender, and Immigrant Life in the U. S. , 1820-1990

Review of: From the Other Side: Women, Gender, and Immigrant Life in the U.S., 1820-1990. Gabaccia, Donna

From the Other Side: Women, Gender, and Immigrant Life in the U. S. , 1820-1990

Review of: From the Other Side: Women, Gender, and Immigrant Life in the U.S., 1820-1990. Gabaccia, Donna

International comparisons of real product, 1820-1990 : an alternative data set

Research funding was provided by the Spanish Ministry of Education Grant PB95-0294 and Fundación Argentaria

The Evolution of the Accretion Disk around 4U 1820-30 During a Superburst

Accretion from a disk onto a collapsed, relativistic star -- a neutron star or black hole -- is the mechanism widely believed to be responsible for the emission from compact X-ray binaries. Because of the extreme spatial resolution required, it is not yet possible to directly observe the evolution or dynamics of the inner parts of the accretion disk where general relativistic effects are dominant. Here, we use the bright X-ray emission from a superburst on the surface of the neutron star 4U 1820-30 as a spotlight to illuminate the disk surface. The X-rays cause iron atoms in the disk to fluoresce, allowing a determination of the ionization state, covering factor and inner radius of the disk over the course of the burst. The time-resolved spectral fitting shows that the inner region of the disk is disrupted by the burst, possibly being heated into a thicker, more tenuous flow, before recovering its previous form in ~1000 s. This marks the first instance that the evolution of the inner regions of an accretion disk has been observed in real-time.Comment: 5 pages, 2 figures, accepted by ApJ Letter

Accretion Rates in X--Ray Bursting Sources

We present estimates for the accretion rates in 13 X--ray bursting sources which exhibit photospheric expansion, basing on theoretical models of stationary, radiatively driven winds from neutron stars. The relatively high values obtained, \Mdot_{acc}\magcir 10^{-9} \MS, are in accordance with theoretical limits for unstable helium burning, and, at the same time, almost never exceed the ``dynamical'' limit for stationary accretion, \sim 10 \Mdot_{Edd}. The only exceptions are 1820-30, already known to be a very peculiar object, and 1608-522; there are indications, however, that in both sources, accretion could be non--stationary.Comment: 21 pages, PlainTe