A Geomorphology of Megaliths: Neolithic Landscapes in the Alto Alentejo, Portugal

The Alentejo region of Portugal is known for a high concentration of Neolithic-aged megalithic monuments: tombs (dolmens or antas) and ceremonial features such as standing stones (menhirs) and stone circles (cromleques). Concentrations of these monuments tend to be found on or near weathered granite terrains. Unloading slabs and remnant corestones appear to be the stones of preference for megalith makers in the Alentejo district of Portugal. Some of the stones may have been imported from distant sources, but most appear to be of local origin. In general, most stones do not appear to have been altered much from their original state as field stones. Weathering tests demonstrate that menhirs are essentially identical to native cornerstones. Many menhirs still exhibit a soil line. The former subaerial side of the stone usually retains a thick growth of lichen, while the soil side remains oxidized. Newly exposed, antas and menhirs now suffer from enhanced weathering and erosion from atmospheric and biological agents. This deterioration is often difficult to discern from the inherited decomposition of pre-megalithic time

The Nature of Boulder-Rich Deposits in the Upper Big Flat Brook Drainage, Sussex County, New Jersey

The upper reaches of the Big Flat Brook drainage, northwest of Kittatinny Mountain, contain a variety of glacial, pro-glacial, and periglacial deposits from the Late Quaternary. The area is dominated by recessional moraines and ubiquitous ground moraine, along with meltwater deposits, drumlins, and possible postglacial periglacial features. We have identified a curious boulder-rich deposit in the vicinity of Lake Ocquittunk and Lake Wapalanne on upper Big Flat Brook. The area where these boulder deposits occur is mapped (1:24,000 surficial geology) as till. As mapped and observed, larger cobbles and boulders within the till are quartz-pebble conglomerate, quartzite, sandstone, and shale. The boulder-rich deposits differ from the typical till, however. Unlike the local till, which is more mixed in lithology, the boulder deposits are nearly exclusively Shawangunk conglomerate. The deposits are discontinuous, but appear to occur at a topographic level above the meltwater stream terraces. The boulders in the deposits lie partially embedded in soil, but are very closely spaced. The boulders range in size from ~20cm to over 100cm, and present a subrounded to subangular shape. There appears to be a fabric orientation of the boulders, NE-SW, with subsidiary orientations. As the boulder deposits differ from other mapped features in the area, we attempt to ascertain the origin for the deposits. Unique moraine dynamics, meltwater flood, periglacial slope movement, and slope-snow bank processes are possible explanations. Detailed examination of these boulder deposits will provide a finer explanation of the glacial and post-glacial geomorphic history of the area

Matrix exponential-based closures for the turbulent subgrid-scale stress tensor

Two approaches for closing the turbulence subgrid-scale stress tensor in terms of matrix exponentials are introduced and compared. The first approach is based on a formal solution of the stress transport equation in which the production terms can be integrated exactly in terms of matrix exponentials. This formal solution of the subgrid-scale stress transport equation is shown to be useful to explore special cases, such as the response to constant velocity gradient, but neglecting pressure-strain correlations and diffusion effects. The second approach is based on an Eulerian-Lagrangian change of variables, combined with the assumption of isotropy for the conditionally averaged Lagrangian velocity gradient tensor and with the recent fluid deformation approximation. It is shown that both approaches lead to the same basic closure in which the stress tensor is expressed as the matrix exponential of the resolved velocity gradient tensor multiplied by its transpose. Short-time expansions of the matrix exponentials are shown to provide an eddy-viscosity term and particular quadratic terms, and thus allow a reinterpretation of traditional eddy-viscosity and nonlinear stress closures. The basic feasibility of the matrix-exponential closure is illustrated by implementing it successfully in large eddy simulation of forced isotropic turbulence. The matrix-exponential closure employs the drastic approximation of entirely omitting the pressure-strain correlation and other nonlinear scrambling terms. But unlike eddy-viscosity closures, the matrix exponential approach provides a simple and local closure that can be derived directly from the stress transport equation with the production term, and using physically motivated assumptions about Lagrangian decorrelation and upstream isotropy

Diagnosis-based risk adjustment for Medicare capitation payments

Using 1991-92 data for a 5-percent Medicare sample, we develop, estimate, and evaluate risk-adjustment models that utilize diagnostic information from both inpatient and ambulatory claims to adjust payments for aged and disabled Medicare enrollees. Hierarchical coexisting conditions (HCC) models achieve greater explanatory power than diagnostic cost group (DCG) models by taking account of multiple coexisting medical conditions. Prospective models predict average costs of individuals with chronic conditions nearly as well as concurrent models. All models predict medical costs far more accurately than the current health maintenance organization (HMO) payment formula

Turbulence Fluctuations and New Universal Realizability Conditions in Modelling

General turbulent mean statistics are shown to be characterized by a variational principle. The variational functionals, or ``effective actions'', have experimental consequences for turbulence fluctuations and are subject to realizability conditions of positivity and convexity. An efficient Rayleigh-Ritz algorithm is available to calculate approximate effective actions within PDF closures. Examples are given for Navier-Stokes and for a 3-mode system of Lorenz. The new realizability conditions succeed at detecting {\em a priori} the poor predictions of PDF closures even when the classical 2nd-order moment realizability conditions are satisfied.Comment: 4 pages, LaTeX (Version 2.09), 3 figures, Postscript, Submitted to Phys. Rev. Let

Using diagnoses to describe populations and predict costs

The Diagnostic Cost Group Hierarchical Condition Category (DCG/HCC) payment models summarize the health care problems and predict the future health care costs of populations. These models use the diagnoses generated during patient encounters with the medical delivery system to infer which medical problems are present. Patient demographics and diagnostic profiles are, in turn, used to predict costs. We describe the logic, structure, coefficients and performance of DCG/HCC models, as developed and validated on three important data bases (privately insured, Medicaid, and Medicare) with more than 1 million people each

Principal inpatient diagnostic cost group model for Medicare risk adjustment

The Balanced Budget Act (BBA) of 1997 required HCFA to implement health-status-based risk adjustment for Medicare capitation payments for managed care plans by January 1, 2000. In support of this mandate, HCFA has been collecting inpatient encounter data from health plans since 1997. These data include diagnoses and other information that can be used to identify chronic medical problems that contribute to higher costs, so that health plans can be paid more when they care for sicker patients. In this article, the authors describe the risk-adjustment model HCFA is implementing in the year 2000, known as the Principal Inpatient Diagnostic Cost Group (PIPDCG) model

Fluctuations in the Irreversible Decay of Turbulent Energy

A fluctuation law of the energy in freely-decaying, homogeneous and isotropic turbulence is derived within standard closure hypotheses for 3D incompressible flow. In particular, a fluctuation-dissipation relation is derived which relates the strength of a stochastic backscatter term in the energy decay equation to the mean of the energy dissipation rate. The theory is based on the so-called ``effective action'' of the energy history and illustrates a Rayleigh-Ritz method recently developed to evaluate the effective action approximately within probability density-function (PDF) closures. These effective actions generalize the Onsager-Machlup action of nonequilibrium statistical mechanics to turbulent flow. They yield detailed, concrete predictions for fluctuations, such as multi-time correlation functions of arbitrary order, which cannot be obtained by direct PDF methods. They also characterize the mean histories by a variational principle.Comment: 26 pages, Latex Version 2.09, plus seceq.sty, a stylefile for sequential numbering of equations by section. This version includes new discussion of the physical interpretation of the formal Rayleigh-Ritz approximation. The title is also change

Bohm and Einstein-Sasaki Metrics, Black Holes and Cosmological Event Horizons

We study physical applications of the Bohm metrics, which are infinite sequences of inhomogeneous Einstein metrics on spheres and products of spheres of dimension 5 <= d <= 9. We prove that all the Bohm metrics on S^3 x S^2 and S^3 x S^3 have negative eigenvalue modes of the Lichnerowicz operator and by numerical methods we establish that Bohm metrics on S^5 have negative eigenvalues too. We argue that all the Bohm metrics will have negative modes. These results imply that higher-dimensional black-hole spacetimes where the Bohm metric replaces the usual round sphere metric are classically unstable. We also show that the stability criterion for Freund-Rubin solutions is the same as for black-hole stability, and hence such solutions using Bohm metrics will also be unstable. We consider possible endpoints of the instabilities, and show that all Einstein-Sasaki manifolds give stable solutions. We show how Wick rotation of Bohm metrics gives spacetimes that provide counterexamples to a strict form of the Cosmic Baldness conjecture, but they are still consistent with the intuition behind the cosmic No-Hair conjectures. We show how the Lorentzian metrics may be created ``from nothing'' in a no-boundary setting. We argue that Lorentzian Bohm metrics are unstable to decay to de Sitter spacetime. We also argue that noncompact versions of the Bohm metrics have infinitely many negative Lichernowicz modes, and we conjecture a general relation between Lichnerowicz eigenvalues and non-uniqueness of the Dirichlet problem for Einstein's equations.Comment: 53 pages, 11 figure