Reproductive strategies of two similar Daphnia species

Cladocerans, like many other invertebrates, continue to grow after beginning to reproduce, and their reproductive capability increases with size. What are the demographic consequences of this strategy of indeterminate growth? Here we present results of laboratory experiments in which we measured reproductive strategies of two large, similar cladoceran species, Daphnia pulex and D. pulicaria under high and moderately limiting food conditions. From the experimental data, we calculated the intrinsic rates of increase r for each reproductive strategy. We also estimated the effect on r of changing the pattern of allocation of biomass to reproduction. The results suggest that the daphnid strategy may represent an evolutionary compromise between strategies that maximize r and strategies that maximize total reproductive output

Ultrasonic nondestructive evaluation of impact-damaged graphite fiber composite

Unidirectional Hercules AS/3501-6 graphite fiber epoxy composites were subjected to repeated controlled low-velocity drop weight impacts in the laminate direction. The degradation was ultrasonically monitored using through-thickness attenuation and a modified stress wave factor (SWF). There appears to be strong correlations between the number of drop-weight impacts, the residual tensile strength, the through-thickness attenuation, and the SWF. The results are very encouraging with respect to the NDE potential of both of these ultrasonic parameters to provide strength characterizations in virgin as well as impact-damaged fiber composite structures

An Analytic Solution of Hydrodynamic Equations with Source Terms in Heavy Ion Collisions

The energy and baryon densities in heavy ion collisions are estimated by analytically solving a 1+1 dimensional hydrodynamical model with source terms. Particularly, a competition between the energy and baryon sources and the expansion of the system is discussed in detail.Comment: LaTeX2e, 7 pages, 4 postscript figures, submitted to Int. J. Mod. Phys.

Effect of excited states and applied magnetic fields on the measured hole mobility in an organic semiconductor

Copyright 2010 by the American Physical Society. Article is available at

Pleistocene occupation of the arid zone in Southeast Australia: Research prospects for the Cooper Creek-Strzelecki Desert Region

Archaeological evidence for the presence of people in southeastern Australia as early as 40,000 years ago in environments substantially different from the Southeast Asian homeland of the initial colonists of Greater Australia has generated much discussion on when and how this remarkable feat of colonisation took place, and what was the nature and pace of adjustment of the early colonists to this new continent (see for example Bowdler 1976; Jones 1979; White and O'Connell 1979). Tied in with this discussion are questions of whether there was one group of colonists or several (see Thorne 1971, 1977), and to what extent they transformed the landscape through their impact on the fauna, flora and landforming processes

Pleistocene Archaeology in the Flinders Range: Research Prospects

This research in the Flinders Range is aimed at extending northward the earlier work by Lampert (1977, 1979, forthcoming), that was directed mainly towards the prehistory of Kangaroo Island and adjacent parts of the South Australian mainland. In that region the early stone industry is known as the Kartan. Presumably Pleistocene in origin, it is characterized by a predominance of heavy core tools, while steep-edged scrapers made on flakes constitute a relatively minor element compared with early industries found elsewhere in Australia. Because of this difference, the Kartan is seen by Lampert as a regional variant of the Australian core tool and scraper tradition. Claims by Cooper (1943) for the presence of the Kartan industry at widespread sites in the Flinders Range prompted our investigation of the region

Predator-mediated genotypic shifts in a prey population: experimental evidence

We demonstrate the effect of fish predation on genotype frequencies in a laboratory population composed of two Daphnia magna clones, with historically contrasting exposures to fish predation. The two clones differed in their responsiveness to predation via differential avoidance/escape behavior. The clone which coexists with fish in nature is more responsive to the presence of a fish predator, while the clone not exposed to fish predation does not exhibit the defensive reaction. Fish caused a rapid (within 18 h) and significant shift in Daphnia clonal composition, from 1:1 to 8:1, in favor of the responsive clone. Genotype-specific defensive abilities (modus defendi) can contribute greatly to the phenomenon of genotype replacement under selective predation