Back to the Future: The Managed Care Revolution

The evolution to a managed care system did not achieve the complete, fundamental change in the health care delivery system that was envisioned by some of its early proponents. As the managed care movement evolved beyond the prepaid group practice model, it focused primarily on methods used to spread the cost of health care services

Dynamics of immersed molecules in superfluids

The dynamics of a molecule immersed in a superfluid medium are considered. Results are derived using a classical hydrodynamic approach followed by canonical quantization. The classical model, a rigid body immersed in incompressible fluid, permits a thorough analysis; its effective Hamiltonian generalizes the usual rigid-rotor Hamiltonian. In contrast to the free rigid rotor, the immersed body is shown to have chaotic dynamics. Quantization of the classical model leads to new and experimentally verifiable features. It is shown, for instance, that chiral molecules can behave as "quantum propellers": the rotational-translational coupling induced by the superfluid leads to a nonzero linear momentum in the ground state. Hydrogen peroxide is a strong candidate for experimental detection of this effect. The signature is a characteristic splitting of rotational absorption lines. The 1_{01} --> 1_{10} line in hydrogen peroxide, for example, is predicted to split into three lines separated by as much as 0.01 cm^{-1}, which is about the experimental linewidth.Comment: 10 pages, 3 figure

Dense packing crystal structures of physical tetrahedra

We present a method for discovering dense packings of general convex hard particles and apply it to study the dense packing behavior of a one-parameter family of particles with tetrahedral symmetry representing a deformation of the ideal mathematical tetrahedron into a less ideal, physical, tetrahedron and all the way to the sphere. Thus, we also connect the two well studied problems of sphere packing and tetrahedron packing on a single axis. Our numerical results uncover a rich optimal-packing behavior, compared to that of other continuous families of particles previously studied. We present four structures as candidates for the optimal packing at different values of the parameter, providing an atlas of crystal structures which might be observed in systems of nano-particles with tetrahedral symmetry

“New Bottles Made with My Crest”: Colonial Bottle Seals from Eastern North America, a Gazetteer and Interpretation

Bottle seals or crests are one of the more intriguing categories of artifacts recovered from historic archaeological sites. These small blobs of glass were applied to the necks or shoulders of bottles. They were embossed with initials, shields, and other insignia. They bear dates, as well as the initials and names of individuals and families, taverns, vineyards, schools, retailers, and military units. Archaeologists seriating blown glass bottles from colonial sites in North America have employed them as important dating tools. They have also been interpreted as status markers. This paper provides a gazetteer of bottles with seals from eastern North America. It also argues that private seals, bottle seals employed by individuals rather than organizations, served as indicators of economic, social, and cultural capital in early America. They provide insights into various aspects of colonial culture, including the creation and maintenance of male identities, membership in elite groups, and knowledge of proper etiquette. Furthermore, the geographic disparities in their distribution serve to highlight the development of distinctive regional cultures. These simple seals provide a window into lifeways in colonial America and the aspirations, behaviors, and connections between the owners of vintages consumed long ago

Broadscale density and aggregation of pelagic birds from circumnavigational survey of the Antarctic Ocean

We analyzed the spatial distribution and habitat relationships of pelagic birds on a circumnavigational cruise of Antarctica. Our analysis focused on two issues. First, we present a quantitative description of the structure of Antarctic seabird assemblages. This descriptive information benefits from a much more longitudinally extensive data set than previously available. Second, we used 18 crossings of the edge of the pack ice and 15 crossings of the continental slope to clarify the spatial relationship between aggregations of pelagic birds and these physical features. Our analysis corroborates the uniformity of bird species composition over the longitudinal range we covered. We found that the habitats with light (2/10 to 6/10 coverage) pack-ice cover had the lowest density and biomass of birds of the four ice habitats (open water, icebergs only, light pack ice, heavy pack ice) surveyed. Even though overall bird abundance was not concentrated at the ice edge, aggregations of individual species were statistically likely to appear there. We found only a slight (34%) elevation in bird biomass over the continental slope, despite repeated previous findings of bird aggregations associated with the Antarctic slope front. Finally, 45% of the seabirds we observed were in three large aggregations. We suggest this concentration demonstrates the importance of localized patches of prey to foraging seabirds in the Antarctic

Random projections and the optimization of an algorithm for phase retrieval

Iterative phase retrieval algorithms typically employ projections onto constraint subspaces to recover the unknown phases in the Fourier transform of an image, or, in the case of x-ray crystallography, the electron density of a molecule. For a general class of algorithms, where the basic iteration is specified by the difference map, solutions are associated with fixed points of the map, the attractive character of which determines the effectiveness of the algorithm. The behavior of the difference map near fixed points is controlled by the relative orientation of the tangent spaces of the two constraint subspaces employed by the map. Since the dimensionalities involved are always large in practical applications, it is appropriate to use random matrix theory ideas to analyze the average-case convergence at fixed points. Optimal values of the gamma parameters of the difference map are found which differ somewhat from the values previously obtained on the assumption of orthogonal tangent spaces.Comment: 15 page

Ocean warming and long-term change in pelagic bird abundance within the California current system

As a result of repeated sampling of pelagic bird abundance over 3 x 105 km2 of open ocean 4 times a year for 8 yr, we report that seabird abundance within the California Current system has declined by 40% over the period 1987 to 1994. This decline has accompanied a concurrent, long-term increase in sea surface temperature. The decline in overall bird abundance is largely, but not entirely, a consequence of the 90% decline of sooty shearwaters Puffinus griseus, the numerically dominant species of the California Current. Seabirds of the offshore waters we sampled showed a different pattern from seabirds of the shelf and slope waters. Leach's storm-petrels Oceanodroma leucorhoa, the commonest species offshore, significantly increased during 1987 to 1994, while sooty shearwaters and other inshore species declined. Thus the clearest pattern that emerges from our data is one of gradual but persistent changes in abundance that transpire at time scales longer than 1 yr. Nevertheless, we did find evidence of change at shorter time scales (weeks and months) that may relate to the El Niño episode of 1992 to 1993: Pronounced positive anomalies of abundance of brown pelicans Pelecanus occidentalis and Heerman's gulls Larus heermani in fall 1991, and black Oceanodroma melania andleast O. microsoma storm-petrels in late summer 1992, likely reflect northward dispersal following reproductive failure in the Gulf of California