Seed Selection by the Harvester Ant Pogonomyrmex rugosus (Hymenoptera: Formicidae) in Coastal Sage Scrub: Interactions With Invasive Plant Species.

Harvester ants can be the dominant seed predators on plants by collecting and eating seeds and are known to influence plant communities. Harvester ants are abundant in coastal sage scrub (CSS), and CSS is frequently invaded by several exotic plant species. This study used observations of foraging and cafeteria-style experiments to test for seed species selection by the harvester ant Pogonomyrmex rugosus Emery (Hymenoptera: Formicidae) in CSS. Analysis of foraging behavior showed that P. rugosus carried seeds of exotic Erodium cicutarium (L.) and exotic Brassica tournefortii (Gouan) on 85 and 15% of return trips to the nest (respectively), and only a very few ants carried the native seeds found within the study areas. When compared with the availability of seeds in the field, P. rugosus selected exotic E. cicutarium and avoided both native Encelia farinosa (Torrey & A. Gray) and exotic B. tournefortii. Foraging by P. rugosus had no major effect on the seed bank in the field. Cafeteria-style experiments confirmed that P. rugosus selected E. cicutarium over other available seeds. Native Eriogonum fasciculatum (Bentham) seeds were even less selected than E. farinosa and B. tournefortii.

Disordered nuclear pasta, magnetic field decay, and crust cooling in neutron stars.

Nuclear pasta, with nonspherical shapes, is expected near the base of the crust in neutron stars. Large-scale molecular dynamics simulations of pasta show long lived topological defects that could increase electron scattering and reduce both the thermal and electrical conductivities. We model a possible low-conductivity pasta layer by increasing an impurity parameter Q_{imp}. Predictions of light curves for the low-mass x-ray binary MXB 1659-29, assuming a large Q_{imp}, find continued late time cooling that is consistent with Chandra observations. The electrical and thermal conductivities are likely related. Therefore, observations of late time crust cooling can provide insight on the electrical conductivity and the possible decay of neutron star magnetic fields (assuming these are supported by currents in the crust).

Subject, project or self? Thoughts on ethical dilemmas for social and medical researchers.

In this paper we address an important but sadly neglected area; namely some of the ethical issues which arise for social and medical researchers in the course of their work. Our concern is for a wide spectrum of researchers using the full range of social research methods from small-scale in-depth qualitative work through to large scale quantitative studies. The unifying factor is that they all have an element of contact and hence the potential for interaction between the researcher and the subject. In our experience (with the exception of some ethnographers) few if any social researchers will have had adequate training about the interactional aspects of their work. As a result they are unprepared for the ethical dilemmas and conflict of loyalties which they might experience. To understand these issues it is important to look at the context within which such research is undertaken.

Structural and cultural determinants of child homicide: a cross-national analysis.

Models of structural characteristics that may influence national infant and child homicide victim rates are derived from prior research. Expected effects of structural characteristics from a "social control" perspective are compared with expected effects from a "guardians, suitable target" perspective. Gartner's (1991) claim that structural factors influence victim rates only in nations with low social insurance expenditures is also evaluated. Statistical analysis of three infant and child age groups with homicide rates from 1965-1969, 1970-1974...1985-1988 fails to support the claim that high and low social insurance expenditure strata differ. Further, no independent effects of Gartner's (1991) three measures of family structure are found. Indicators of family stress/resources, female status, the culture of violence, and a proxy for unmeasured variables and measurement error all contribute to produce high levels of explained variance in each age group.

Relationship of ST-segment elevation to eventual QRS loss in acute anterior wall myocardial infarction.

The position of electrocardiographic ST-segment elevation in acute myocardial infarction (MI) is related to the region of infarction, but the relationship between the initial ST-segment elevation and the eventual loss of QRS voltage remains uncertain. The authors examined body surface map data in 76 patients with acute anterior wall MI to clarify this relationship. The patients had no evidence of previous MI, no subsequent MI, and did not receive thrombolytic therapy or other acute interventions. Maps were recorded on admission to the hospital, every 24 hours during the hospital stay, and again at follow-up examinations 6-48 months after the index MI. The region of ST-segment elevation on the initial body surface map was compared to the region of developed voltage loss in the QRS complex as measured by the integral 0-30, 0-40, 0-80, and 30-80 ms body surface maps subsequently recorded 24 hours, 48 hours, and over 6 months after the initial body surface map. There was a relationship between the position of the ST-segment elevation and the loss of the QRS segment voltages, which was pronounced early after acute MI and diminished months after the MI. The region of ST-segment elevation in the initial body surface map predicts the QRS loss. In the integral QRS0-30 map versus the initial ST-segment map the mean correlation coefficient was -0.54 +/- 0.33 with a median value of -0.67. The integral QRS0-40 map and ST-segment map had a mean correlation coefficient of 0.60 +/- 0.29 and median of 0.66. The mean correlation coefficient is less for the integral QRS0-80 map and nonexistent in the integral QRS30-80 map. This method may be useful for monitoring acute interventions in acute MI.