An improved method of supercharged transposed latissimus dorsi flap with the skin paddle for the management of a complicated lumbosacral defect

OBJECTIVE: Treatment of nonhealing wounds of lower back often poses a powerful challenge. We present one of the first report of treatment of a lumbosacral defect with a supercharged latissimus dorsi flap with the skin paddle. CASE REPORT: We report a case of a 59 yearold man with myeloma of the sacral spine who underwent radiotherapy and chemotherapy and subsequently, laminectomies and placement of hardware for ongoing paresis and spine instability. Then, he developed an open wound and osteomyelitis of the spine with culture positive tuberculous granulomas. After multiple surgical debridement, he presented to our service and was treated with a single stage debridement followed by the performance of a latissimus dorsi musculocutaneous flap based on paraspinal perforators and supercharged. RESULTS: This solution, allowed for augmentation of blood flow to the muscle with the inferior gluteal artery, provided coverage of the defect resistant to the pressure, and simplified post-operative management of the patient. CONCLUSIONS: Alternative treatment options, including free tissue transfer, posed difficulties in finding suitable recipient vessels near the defect, in inserting the flap so as to restore its original length without compromising blood flow, and in postoperative care of the patient. Treatment of a lumbosacral defect with a supercharged latissimus dorsi flap with the skin paddle may represent a milestone procedure for complicated lower spine wounds

Induced scalarization in boson stars and scalar gravitational radiation

The dynamical evolution of boson stars in scalar-tensor theories of gravity is considered in the physical (Jordan) frame. We focus on the study of spontaneous and induced scalarization, for which we take as initial data configurations on the well-known S-branch of a single boson star in general relativity. We show that during the scalarization process a strong emission of scalar radiation occurs. The new stable configurations (S-branch) of a single boson star within a particular scalar-tensor theory are also presented.Comment: 18 pages, 11 figures. Minor changes to match the published versio

Generalized harmonic spatial coordinates and hyperbolic shift conditions

We propose a generalization of the condition for harmonic spatial coordinates analogous to the generalization of the harmonic time slices introduced by Bona et al., and closely related to dynamic shift conditions recently proposed by Lindblom and Scheel, and Bona and Palenzuela. These generalized harmonic spatial coordinates imply a condition for the shift vector that has the form of an evolution equation for the shift components. We find that in order to decouple the slicing condition from the evolution equation for the shift it is necessary to use a rescaled shift vector. The initial form of the generalized harmonic shift condition is not spatially covariant, but we propose a simple way to make it fully covariant so that it can be used in coordinate systems other than Cartesian. We also analyze the effect of the shift condition proposed here on the hyperbolicity of the evolution equations of general relativity in 1+1 dimensions and 3+1 spherical symmetry, and study the possible development of blow-ups. Finally, we perform a series of numerical experiments to illustrate the behavior of this shift condition.Comment: 18 pages and 12 figures, extensively revised version explaining in the new Section IV how the shift condition can be made 3-covarian

The Cauchy problem of scalar-tensor theories of gravity

The 3+1 formulation of scalar-tensor theories of gravity (STT) is obtained in the physical (Jordan) frame departing from the 4+0 covariant field equations. Contrary to the common belief (folklore), the new system of ADM-like equations shows that the Cauchy problem of STT is well formulated (in the sense that the whole system of evolution equations is of first order in the time-derivative). This is the first step towards a full first order (in time and space) formulation from which a subsequent hyperbolicity analysis (a well-posedness determination) can be performed. Several gauge (lapse and shift) conditions are considered and implemented for STT. In particular, a generalization of the harmonic gauge for STT allows us to prove the well posedness of the STT using a second order analysis which is very similar to the one used in general relativity. Some spacetimes of astrophysical and cosmological interest are considered as specific applications. Several appendices complement the ideas of the main part of the paper.Comment: 29 pages Revtex; typos corrected; references added and updated; a shorter version of this paper was published in Classical and Quantum Gravit

A comment on "The Cauchy problem of f(R)- gravity", Class. Quantum Grav., 24, 5667 (2007), arXiv:0709.4414

A critical comment on [N. Lanahan--Tremblay and V. Faraoni, 2007, {\it Class. Quantum Grav.}, {\bf 24}, 5667, arXiv:0709.4414] is given discussing the well-formulation of the Chauchy problem for $f(R)$-gravity in metric-affine theories.Comment: 3 page

Numerical approach for high precision 3-D relativistic star models

A multi-domain spectral method for computing very high precision 3-D stellar models is presented. The boundary of each domain is chosen in order to coincide with a physical discontinuity (e.g. the star's surface). In addition, a regularization procedure is introduced to deal with the infinite derivatives on the boundary that may appear in the density field when stiff equations of state are used. Consequently all the physical fields are smooth functions on each domain and the spectral method is absolutely free of any Gibbs phenomenon, which yields to a very high precision. The power of this method is demonstrated by direct comparison with analytical solutions such as MacLaurin spheroids and Roche ellipsoids. The relative numerical error reveals to be of the order of $10^{-10}$. This approach has been developed for the study of relativistic inspiralling binaries. It may be applied to a wider class of astrophysical problems such as the study of relativistic rotating stars too.Comment: Minor changes, Phys. Rev. D in pres

Effects of Strong Magnetic Fields on Neutron Star Structure

We study static neutron stars with poloidal magnetic fields and a simple class of electric current distributions consistent with the requirement of stationarity. For this class of electric current distributions, we find that magnetic fields are too large for static configurations to exist when the magnetic force pushes a sufficient amount of mass off-center that the gravitational force points outward near the origin in the equatorial plane. (In our coordinates an outward gravitational force corresponds to $\partial\ln g_{tt}/\partial r>0$, where $t$ and $r$ are respectively time and radial coordinates and $g_{tt}$ is coefficient of $dt^2$ in the line element.) For the equations of state (EOSs) employed in previous work, we obtain configurations of higher mass than had been reported; we also present results with more recent EOSs. For all EOSs studied, we find that the maximum mass among these static configurations with magnetic fields is noticeably larger than the maximum mass attainable by uniform rotation, and that for fixed values of baryon number the maximum mass configurations are all characterized by an off-center density maximum.Comment: Submitted to the Astrophysical Journal. 37 pages, 8 figures, uses aastex macro

The Emerging QCD Frontier: The Electron Ion Collider

The self-interactions of gluons determine all the unique features of QCD and lead to a dominant abundance of gluons inside matter already at moderate $x$. Despite their dominant role, the properties of gluons remain largely unexplored. Tantalizing hints of saturated gluon densities have been found in $e$+p collisions at HERA, and in d+Au and Au+Au collisions at RHIC. Saturation physics will have a profound influence on heavy-ion collisions at the LHC. But unveiling the collective behavior of dense assemblies of gluons under conditions where their self-interactions dominate will require an Electron-Ion Collider (EIC): a new facility with capabilities well beyond those In this paper I outline the compelling physics case for $e$+A collisions at an EIC and discuss briefly the status of machine design concepts. of any existing accelerator.Comment: 11 pages, 9 figures, prepared for 20th International Conference on Ultra-Relativistic Nucleus-Nucleus Collisions: Quark Matter 2008 (QM2008), Jaipur, India, 4-10 Feb. 200

Hyperbolicity of the Kidder-Scheel-Teukolsky formulation of Einstein's equations coupled to a modified Bona-Masso slicing condition

We show that the Kidder-Scheel-Teukolsky family of hyperbolic formulations of the 3+1 evolution equations of general relativity remains hyperbolic when coupled to a recently proposed modified version of the Bona-Masso slicing condition.Comment: 4 pages. Several changes. Main corrections are in eqs. 4.9 and 4.1

Theoretical Overview Quark Matter '04

The much wider transverse-momentum range accessible in heavy-ion collisions at RHIC and at the LHC allows us to disentangle the dynamics of partonic equilibration from the dynamics of delayed hadronization. This provides a novel tool for testing the equilibration mechanisms underlying QCD thermodynamics. Here, I argue, on the basis of simple formation-time arguments, why this is so, and I review recent theoretical developments in this context.Comment: 12 pages, Latex, 3 eps figures, invited introductory talk at Quark Matter 2004, Oakland, January 11-17, 200