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Sixteen and 64-MDCT have low sensitivity for detecting PI and PDI, while exhibiting a high specificity for PDI. Their use as decision-making tools for the nonoperative management of PI are, therefore, limited.

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Recent theories of the structure of solid hydrogen at high pressure have tended to focus on the hexagonal close-packed (hcp) class of structures typical of low pressure, the contribution of the zero-point motion often being neglected. Here we examine the energy of solid hydrogen at high pressure in different structures, using density-functional theory augmented by the self-consistent harmonic approximation. Above a relative compression ρ/ρ0 ∼ 9 we report an orthorhombic structure, Cmca, that has lower energy (both static and zero-point) than the lowest-energy hcp structures, indicative of a possible layering or martensitic transition occurring in the vicinity of the recently observed high infrared activity.c Les Editions de Physique( 1 ) We have examined the structure proposed by Tse and Klug, and for fully converged calculations we find nearby structures that have significantly lower energies.

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The objectives of our study were to describe a new CT sign of diaphragmatic injury, the "dangling diaphragm" sign, and assess its comparative utility relative to other signs in the diagnosis of diaphragmatic injury resulting from blunt trauma. CT scans of 16 blunt trauma patients (12 men and four women, mean age 36.6 years old) with surgically proven diaphragmatic injury and 32 blunt trauma patients (24 men and eight women; mean age 37.4 years old) without evidence of diaphragmatic injury at surgery were blindly reviewed by three board certified radiologists specializing in body imaging. Studies were evaluated for the presence of established signs of diaphragmatic injury, as well as the dangling diaphragm sign, in which the free edge of the torn hemidiaphragm curls inward from its normal course parallel to the body wall. The sensitivity and specificity of each sign were determined, as were the correlation between the signs and the interobserver agreement in evaluation of these findings. The radiologists' overall impression as to whether rupture was present was also recorded. In select cases, coronal and/or sagittal reformatted images were available, and they were reviewed following evaluation of the original axial images. Any change in interpretation due to these images was noted. The sensitivity of the radiologists' overall impression for detection of diaphragmatic injury was 77%, with 98% specificity. Individual signs of diaphragmatic injury had sensitivities ranging from 44% to 69%, with specificities of 98% to 100%. The dangling diaphragm sign had a sensitivity of 54% and a specificity of 98%, similar to the other signs. Multiple signs were present in most cases of diaphragmatic injury, and coronal and sagittal reformatted images had little impact. Diaphragmatic injury remains a challenging radiographic diagnosis. The dangling diaphragm is a conspicuous sign of diaphragmatic injury, and awareness of it may increase detection of diaphragmatic injury on CT studies.

By increase in density, impelled by pressure, the electronic energy bands in dense hydrogen attain significant widths. Nevertheless, arguments can be advanced suggesting that a physically consistent description of the general consequences of this electronic structure can still be constructed from interacting but state-dependent multipoles. These reflect, in fact self-consistently, a disorder-induced localization of electron states partially manifesting the effects of proton dynamics; they retain very considerable spatial inhomogeneity (as they certainly do in the molecular limit). This description, which is valid provided that an overall energy gap has not closed, leads at a mean-field level to the expected quadrupolar coupling, but also for certain structures to the eventual emergence of dipolar terms and their coupling when a state of broken charge symmetry is developed. A simple Hamiltonian incorporating these basic features then leads to a high-density, low-temperature phase diagram that appears to be in substantial agreement with experiment. In particular, it accounts for the fact that whereas the phase I-II phase boundary has a significant isotope dependence, the phase II-III boundary has very little.A t low temperatures and ordinary pressure, crystalline hydrogen has a mean electronic density that exceeds the valence electron density of all the alkali metals and even the alkaline earths under equivalent conditions. However, it is a ground state insulator retaining this physical characteristic at densities an entire order of magnitude higher than its one atmosphere value. Under these compressions application of band theory for rigorously static lattices shows clearly that the electronic energy bands of hydrogen are appreciably wide, indicating significant overlap between the standard orbitals invoked to describe the low density phases. Yet much of the electronic charge remains well localized in the vicinity of a Bohr radius from the protons, and there is evidence that the currently accessible part of the low temperature, high density phase diagram can still be understood in terms of interactions originating with multipole expansions associated with effectively localized states and a continuing preservation of the strongly inhomogeneous character of the microscopic electron density e (1) (r). The deeper understanding of this notion, and its consequences, constitutes the bulk of what follows, but starting from an elementary observation that a macroscopic neutral quantity of hydrogen is but a dual Fermion assembly of electrons and protons, and that the dynamics of the latter have considerable influence on the former. The Dense Hydrogen ProblemThe quantum mechanics of N(ϳ10 23 ) electrons in a uniform compensating charged continuum of volume V is a well studied problem, though debate still continues on the nature of its low density states (especially in reduced dimensionality). If v c (r) ϭ e 2 ͞r is the fundamental Coulomb interaction, and if e ϭ e(N͞V) is the corresponding rigid continuum charge density, the...