A Hybrid Godunov Method for Radiation Hydrodynamics

From a mathematical perspective, radiation hydrodynamics can be thought of as a system of hyperbolic balance laws with dual multiscale behavior (multiscale behavior associated with the hyperbolic wave speeds as well as multiscale behavior associated with source term relaxation). With this outlook in mind, this paper presents a hybrid Godunov method for one-dimensional radiation hydrodynamics that is uniformly well behaved from the photon free streaming (hyperbolic) limit through the weak equilibrium diffusion (parabolic) limit and to the strong equilibrium diffusion (hyperbolic) limit. Moreover, one finds that the technique preserves certain asymptotic limits. The method incorporates a backward Euler upwinding scheme for the radiation energy density and flux as well as a modified Godunov scheme for the material density, momentum density, and energy density. The backward Euler upwinding scheme is first-order accurate and uses an implicit HLLE flux function to temporally advance the radiation components according to the material flow scale. The modified Godunov scheme is second-order accurate and directly couples stiff source term effects to the hyperbolic structure of the system of balance laws. This Godunov technique is composed of a predictor step that is based on Duhamel's principle and a corrector step that is based on Picard iteration. The Godunov scheme is explicit on the material flow scale but is unsplit and fully couples matter and radiation without invoking a diffusion-type approximation for radiation hydrodynamics. This technique derives from earlier work by Miniati & Colella 2007. Numerical tests demonstrate that the method is stable, robust, and accurate across various parameter regimes.Comment: accepted for publication in Journal of Computational Physics; 61 pages, 15 figures, 11 table

Imaging sub-milliarcsecond stellar features with intensity interferometry using air Cherenkov telescope arrays

Recent proposals have been advanced to apply imaging air Cherenkov telescope arrays to stellar intensity interferometry (SII). Of particular interest is the possibility of model-independent image recovery afforded by the good (u, v)-plane coverage of these arrays, as well as recent developments in phase retrieval techniques. The capabilities of these instruments used as SII receivers have already been explored for simple stellar objects, and here the focus is on reconstructing stellar images with non-uniform radiance distributions. We find that hot stars (T > 6000 K) containing hot and/or cool localized regions (T \sim 500 K) as small as \sim 0.1 mas can be imaged at short wavelengths ({\lambda} = 400 nm).Comment: Accepted for publication in MNRAS. 6 pages, 10 figure

Stellar Wind Accretion in GX301-2: Evidence for a High-density Stream

The X-ray binary system GX301-2 consists of a neutron star in an eccentric orbit accreting from the massive early-type star WRAY 977. It has previously been shown that the X-ray orbital light curve is consistent with existence of a gas stream flowing out from Wray 977 in addition to its strong stellar wind. Here, X-ray monitoring observations by the Rossi X-ray Timing Explorer (RXTE)/ All-Sky-Monitor (ASM) and pointed observations by the RXTE/ Proportional Counter Array (PCA) over the past decade are analyzed. We analyze both the flux and column density dependence on orbital phase. The wind and stream dynamics are calculated for various system inclinations, companion rotation rates and wind velocities, as well as parametrized by the stream width and density. These calculations are used as inputs to determine both the expected accretion luminosity and the column density along the line-of-sight to the neutron star. The model luminosity and column density are compared to observed flux and column density vs. orbital phase, to constrain the properties of the stellar wind and the gas stream. We find that the change between bright and medium intensity levels is primarily due to decreased mass loss in the stellar wind, but the change between medium and dim intensity levels is primarily due to decreased stream density. The mass-loss rate in the stream exceeds that in the stellar wind by a factor of 2.5. The quality of the model fits is significantly better for lower inclinations, favoring a mass for WRAY 977 of 53 to 62 Msun.Comment: 19 pages, 6 figure

Connective tissue activation. xxxvi. the origin, variety, distribution, and biologic fate of connective tissue activating peptide–iii isoforms: characteristics in patients with rheumatic, renal, and arterial disease

Objective. To determine the origin, distribution, and biologic fate of platelet-derived connective tissue activating peptide–III (CTAP-III), to define the relative amounts of the antigen forms (CTAP-III, betathromboglobulin [Β-TG], neutrophil activating peptide–2 [NAP-2]) in plasma of normal persons and those with rheumatic or end-stage renal disease, and to define the isoforms of CTAP-III in platelets, plasma, transudates, and tissue deposits. Methods. CTAP-III in plasma was measured by enzyme-linked immunosorbent assay, and growth promoting activity of CTAP-III isoforms was tested in synovial and peritoneal cell cultures by measuring increased synthesis of 14 C-glycosaminoglycan ( 14 C-GAG) and 3 H-DNA. Isolated CTAP-III was characterized by Western blotting, microsequencing, and mass spectrometry. Results. CTAP-III was the primary isoform of this antigen family in normal platelets and platelet-rich plasma; Β-TG and NAP-2 accounted for 90%), and Β-TG was the most rare (0–1%). Deposition of CTAP-III in tissues, such as synovium, spleen, and kidney, is associated with partial processing to NAP-2–like isoforms and the potential to induce neutrophil and fibroblast activation in patients with rheumatic or end-stage renal disease.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/37798/1/1780360816_ftp.pd

Hernioplastía Inguinal Electiva

Antecedentes: La hernioplastía es la técnica más utilizada para reparar la hernia inguinal.Objetivos: determinar las características demográficas, tipos de hernia, clasificación y resultados de la cirugía.Pacientes y Método: Serie de 229 pacientes sometidos a hernioplastia inguinal electiva en la Primera Cátedra de Clínica Quirúrgica en el periodo 2005–2009; estudio descriptivo retrospectivo longitudinal con las siguientes variables: características demográficas, co-morbilidad, tipo de hernia, clasificación de Gilbert, modalidad de reparación y resultados inmediatos.Resultados: La edad media fue de 46 años y 90 % eran varones; la hernia era indirecta en 84%, directa en 7% y mixtas en 5%. En 112 casos la hernia se situaba a la derecha, en 99 a la izquierda y en 18 bilateral. Se encontró hipertensión arterial en 46 pacientes, cardiopatía hipertensiva en 8, cardiopatía isquémica en 2, tabaquismo 5 y diabetes mellitus en 2 ; 10 pacientes tenían hipertrofia prostática, 5 asma o alergia a medicamentos y 5 trastornos psiquiátricos ; 18% correspondían al tipo I de Gilbert, 45% al tipo II, 18% al III, 4% al IV, 8% al V y el restante tipo VI y VII. Se empleó la técnica del Plugstein en 207 pacientes y la técnica de Lichtenstein en 22. Las complicaciones fueron: hematoma en 3 y seroma en 2. Un paciente desarrolló infección del sitio quirúrgico. Una recidiva precoz fue comprobada en 3 pacientes (1.3%).Conclusiones: la hernia inguinal es más frecuente en la 5a década y en el sexo masculino. La variedad más frecuente es la indirecta y la mayoría son de tipo II de Gilbert. La hernioplastia electiva permite obtener resultados inmediatos satisfactorios, con escasa recidiva

A dynamical magnetosphere model for periodic Halpha emission from the slowly rotating magnetic O star HD191612

The magnetic O-star HD191612 exhibits strongly variable, cyclic Balmer line emission on a 538-day period. We show here that its variable Halpha emission can be well reproduced by the rotational phase variation of synthetic spectra computed directly from full radiation magneto-hydrodynamical simulations of a magnetically confined wind. In slow rotators such as HD191612, wind material on closed magnetic field loops falls back to the star, but the transient suspension of material within the loops leads to a statistically overdense, low velocity region around the magnetic equator, causing the spectral variations. We contrast such "dynamical magnetospheres" (DMs) with the more steady-state "centrifugal magnetospheres" of stars with rapid rotation, and discuss the prospects of using this DM paradigm to explain periodic line emission from also other non-rapidly rotating magnetic massive stars.Comment: 5 pages, 5 figures, accepted for publication in MNRAS letter

A hydrodynamic scheme for two-component winds from hot stars

We have developed a time-dependent two-component hydrodynamics code to simulate radiatively-driven stellar winds from hot stars. We use a time-explicit van Leer scheme to solve the hydrodynamic equations of a two-component stellar wind. Dynamical friction due to Coulomb collisions between the passive bulk plasma and the line-scattering ions is treated by a time-implicit, semi-analytic method using a polynomial fit to the Chandrasekhar function. This gives stable results despite the stiffness of the problem. This method was applied to model stars with winds that are both poorly and well-coupled. While for the former case we reproduce the mCAK solution, for the latter case our solution leads to wind decoupling.Comment: accepted to Astronomy and Astrophysic

Numerical simulations of super-luminous supernovae of type IIn

We present numerical simulations that include 1-D Eulerian multi-group radiation-hydrodynamics, 1-D non-LTE radiative transfer, and 2-D polarised radiative transfer for super-luminous interacting supernovae (SNe). Our reference model is a ~10Msun inner shell with 10^51erg ramming into a ~3Msun cold outer shell (the circumstellar-medium, or CSM) that extends from 10^15cm to 2x10^16cm and moves at 100km/s. We discuss the light curve evolution, which cannot be captured adequately with a grey approach. In these interactions, the shock-crossing time through the optically-thick CSM is much longer than the photon diffusion time. Radiation is thus continuously leaking from the shock through the CSM, in disagreement with the shell-shocked model that is often invoked. Our spectra redden with time, with a peak distribution in the near-UV during the first month gradually shifting to the optical range over the following year. Initially Balmer lines exhibit a narrow line core and the broad line wings that are characteristic of electron scattering in the SNe IIn atmospheres (CSM). At later times they also exhibit a broad blue shifted component which arises from the cold dense shell. Our model results are broadly consistent with the bolometric light curve and spectral evolution observed for SN2010jl. Invoking a prolate pole-to-equator density ratio in the CSM, we can also reproduce the ~2% continuum polarisation, and line depolarisation, observed in SN2010jl. By varying the inner shell kinetic energy and the mass and extent of the outer shell, a large range of peak luminosities and durations, broadly compatible with super-luminous SNe IIn like 2010jl or 2006gy, can be produced.Comment: paper accepted to MNRA

Costo/beneficio de la profilaxis antibiótica en la hernioplastia inguinal electiva

Introducción: el empleo sistemático de antibióticos es generalmente aceptado como factorimportante en la prevención de las infecciones del sitio operatorio. Objetivo: Estudiar la relacióncosto/beneficio del empleo sistemático de la profilaxis antibiótica en la cirugía electiva de la herniainguinal, con empleo de material protésico. Material y métodos: 229 casos de hernioplastíainguinal electiva efectuadas en la Primera Cátedra de Clínica Quirúrgica, FCM-UNA en el periodo2005-2009 fueron seleccionados para un estudio retrospectivo descriptivo de corte transversocon componente analítico. Las variables fueron: empleo de antibióticos, frecuencia de infección delsitio operatorio, relación infección/empleo de antibióticos, costo de los medicamentos y costo de lainfección postoperatoria. Resultados: la profilaxis fue adecuada en tiempo y dosis en el 29% delos casos; la frecuencia de la infección fue del 0.4%, sin diferencias entre los que recibieronprofilaxis y los que nó (0.8 y 0.6%); el uso de antibióticos incrementó los costos muy escasamentepero la infección los aumentó notablemente. Conclusión: no se encontró diferencia alguna en lafrecuencia de infección relacionada con el empleo de antibióticos; los costos de la medicaciónprofiláctica son bajos, por lo que la relación costo beneficio no justifica su emple

Dynamical Simulations of Magnetically Channeled Line-Driven Stellar Winds: II. The Effects of Field-Aligned Rotation

Building upon our previous MHD simulation study of magnetic channeling in radiatively driven stellar winds, we examine here the additional dynamical effects of stellar {\em rotation} in the (still) 2-D axisymmetric case of an aligned dipole surface field. In addition to the magnetic confinement parameter $\eta_{\ast}$ introduced in Paper I, we characterize the stellar rotation in terms of a parameter $W \equiv V_{\rm{rot}}/V_{\rm{orb}}$ (the ratio of the equatorial surface rotation speed to orbital speed), examining specifically models with moderately strong rotation $W =$ 0.25 and 0.5, and comparing these to analogous non-rotating cases. Defining the associated Alfv\'{e}n radius R_{\rm{A}} \approx \eta_{\ast}^{1/4} \Rstar and Kepler corotation radius R_{\rm{K}} \approx W^{-2/3} \Rstar, we find rotation effects are weak for models with $R_{\rm{A}} < R_{\rm{K}}$, but can be substantial and even dominant for models with R_{\rm{A}} \gtwig R_{\rm{K}}. In particular, by extending our simulations to magnetic confinement parameters (up to $\eta_{\ast} = 1000$) that are well above those ($\eta_{\ast} = 10$) considered in Paper I, we are able to study cases with $R_{\rm{A}} \gg R_{\rm{K}}$; we find that these do indeed show clear formation of the {\em rigid-body} disk predicted in previous analytic models, with however a rather complex, dynamic behavior characterized by both episodes of downward infall and outward breakout that limit the buildup of disk mass. Overall, the results provide an intriguing glimpse into the complex interplay between rotation and magnetic confinement, and form the basis for a full MHD description of the rigid-body disks expected in strongly magnetic Bp stars like $\sigma$ Ori E.Comment: 14 pp, visit this http://shayol.bartol.udel.edu/massivewiki-media/publications/rotation.pdf for full figure version of the paper. MNRAS, in pres