238 research outputs found
General Relativistic MHD Simulations of the Gravitational Collapse of a Rotating Star with Magnetic Field as a Model of Gamma-Ray Bursts
We have performed 2.5-dimensional general relativistic magnetohydrodynamic
(MHD) simulations of the gravitational collapse of a magnetized rotating
massive star as a model of gamma ray bursts (GRBs). This simulation showed the
formation of a disk-like structure and the generation of a jet-like outflow
inside the shock wave launched at the core bounce. We have found the jet is
accelerated by the magnetic pressure and the centrifugal force and is
collimated by the pinching force of the toroidal magnetic field amplified by
the rotation and the effect of geometry of the poloidal magnetic field. The
maximum velocity of the jet is mildly relativistic ( 0.3 c).Comment: 4 pages, 1 figure, aipTEX, contribution to the 2003 GRB Conference,
held at Santa Fe, N
Task Scheduling Algorithm for Multicore Processor Systems with Turbo Boost and Hyper-Threading
PDPTA'14 : The 2014 International Conference on Parallel and Distributed Processing Techniques and Applications , Jul 21-24, 2014 , Las Vegas, NV, USAIn this paper, we propose a task scheduling algorithm for multiprocessor systems with Turbo Boost and Hyper-Threading technologies. The proposed algorithm minimizes the total computation time taking account of dynamic changes of the processing speed by the two technologies, in addition to the network contention among the processors. We constructed a clock speed model with which the changes of processing speed with Turbo Boost and Hyper-threading can be estimated for various processor usage patterns. We then constructed a new scheduling algorithm that minimizes the total execution time of a task graph considering network contention and the two technologies. We evaluated the proposed algorithm by simulations and experiments with a multi-processor system consisting of 4 PCs. In the experiment, the proposed algorithm produced a schedule that reduces the total execution time by 36% compared to conventional methods which are straightfor-ward extensions of an existing method
Control of STING Agonistic/Antagonistic Activity Using Amine-Skeleton-Based c-di-GMP Analogues
Stimulator of Interferon Genes (STING) is a type of endoplasmic reticulum (ER)-membrane receptor. STING is activated by a ligand binding, which leads to an enhancement of the immune-system response. Therefore, a STING ligand can be used to regulate the immune system in therapeutic strategies. However, the natural (or native) STING ligand, cyclic-di-nucleotide (CDN), is unsuitable for pharmaceutical use because of its susceptibility to degradation by enzymes and its low cell-membrane permeability. In this study, we designed and synthesized CDN derivatives by replacing the sugar-phosphodiester moiety, which is responsible for various problems of natural CDNs, with an amine skeleton. As a result, we identified novel STING ligands that activate or inhibit STING. The cyclic ligand 7, with a cyclic amine structure containing two guanines, was found to have agonistic activity, whereas the linear ligand 12 showed antagonistic activity. In addition, these synthetic ligands were more chemically stable than the natural ligands
General Relativistic Magnetohydrodynamic Simulations of Collapsars
We have performed 2.5-dimensional general relativistic magnetohydrodynamic
(MHD) simulations of the gravitational collapse of a magnetized rotating
massive star as a model of gamma ray bursts (GRBs). The current calculation
focuses on general relativistic MHD with simplified microphysics (we ignore
neutrino cooling, physical equation of state, and photodisintegration).
Initially, we assume that the core collapse has failed in this star. A few
black hole is inserted by hand into the calculation. The
simulations presented in the paper follow the accretion of gas into a black
hole that is assumed to have formed before the calculation begins.The
simulation results show the formation of a disk-like structure and the
generation of a jetlike outflow inside the shock wave launched at the core
bounce. We have found that the jet is accelerated by the magnetic pressure and
the centrifugal force and is collimated by the pinching force of the toroidal
magnetic field amplified by the rotation and the effect of geometry of the
poloidal magnetic field. The maximum velocity of the jet is mildly relativistic
(0.3c). The velocity of the jet becomes larger as the initial rotational
velocity of stellar matter gets faster. On the other hand, the dependence on
the initial magnetic field strength is a bit more complicated: the velocity of
the jet increases with the initial field strength in the weak field regime,
then is saturated at some intermediate field strength, and decreases beyond the
critical field strength. These results are related to the stored magnetic
energy determined by the balance between the propagation time of the Alfven
wave and the rotation time of the disk (or twisting time).Comment: 36 pages, 2 tables, 15 figures, ApJ May 2004, in pres
Successful Treatment of Staphylococcus schleiferi Infection after Aortic Arch Repair: In Situ Aortic Arch Replacement and Domino Reconstruction of the Debranching Graft using Autologous Iliac Artery
A 62-year-old Japanese male presented with graft infection by Staphylococcus schleiferi 50 days after debranching of the left subclavian artery and frozen elephant trunk repair for the entry closure of a Stanford type B aortic dissection. The graft was removed, and the patient was successfully treated using in situ reconstruction of the arch with omental flap coverage, removal of the debranching graft, autologous iliac artery grafting, and longterm antibiotics. Domino reconstruction of the infected debranching graft using autologous external iliac artery and a Dacron graft can thus be a good option in similar cases
Multi log-normal density structure in Cygnus-X molecular clouds: A fitting for N-PDF without power-law
We studied the H column density probability distribution function (N-PDF)
based on molecular emission lines using the Nobeyama 45-m Cygnus X CO survey
data. Using the DENDROGRAM and SCIMES algorithms, we identified 124 molecular
clouds in the CO data. From these identified molecular clouds, an N-PDF
was constructed for 11 molecular clouds with an extent of more than 0.4
deg. From the fitting of the N-PDF, we found that the N-PDF could be
well-fitted with one or two log-normal distributions. These fitting results
provided an alternative density structure for molecular clouds from a
conventional picture. We investigated the column density, dense molecular cloud
cores, and radio continuum source distributions in each cloud and found that
the N-PDF shape was less correlated with the star-forming activity over a whole
cloud. Furthermore, we found that the log-normal N-PDF parameters obtained from
the fitting showed two impressive features. First, the log-normal distribution
at the low-density part had the same mean column density ( 10
cm) for almost all the molecular clouds. Second, the width of the
log-normal distribution tended to decrease with an increasing mean density of
the structures. These correlations suggest that the shape of the N-PDF reflects
the relationship between the density and turbulent structure of the whole
molecular cloud but is less affected by star-forming activities.Comment: 14 pages, 7 Figures, Accepted in MNRA
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