The effect of adipose-derived stem cell sheets and CTGF on early flexor tendon healing in a canine model

Oral History interview of Curt Sawyer. Interview conducted by Robin Dunn

Symmetric hyperbolic system in the Ashtekar formulation

We present a first-order symmetric hyperbolic system in the Ashtekar formulation of general relativity for vacuum spacetime. We add terms from constraint equations to the evolution equations with appropriate combinations, which is the same technique used by Iriondo, Leguizam\'on and Reula [Phys. Rev. Lett. 79, 4732 (1997)]. However our system is different from theirs in the points that we primarily use Hermiticity of a characteristic matrix of the system to characterize our system "symmetric", discuss the consistency of this system with reality condition, and show the characteristic speeds of the system.Comment: 4 pages, RevTeX, to appear in Phys. Rev. Lett., Comments added, refs update

Illustrating Stability Properties of Numerical Relativity in Electrodynamics

We show that a reformulation of the ADM equations in general relativity, which has dramatically improved the stability properties of numerical implementations, has a direct analogue in classical electrodynamics. We numerically integrate both the original and the revised versions of Maxwell's equations, and show that their distinct numerical behavior reflects the properties found in linearized general relativity. Our results shed further light on the stability properties of general relativity, illustrate them in a very transparent context, and may provide a useful framework for further improvement of numerical schemes.Comment: 5 pages, 2 figures, to be published as Brief Report in Physical Review

Advantages of modified ADM formulation: constraint propagation analysis of Baumgarte-Shapiro-Shibata-Nakamura system

Several numerical relativity groups are using a modified ADM formulation for their simulations, which was developed by Nakamura et al (and widely cited as Baumgarte-Shapiro-Shibata-Nakamura system). This so-called BSSN formulation is shown to be more stable than the standard ADM formulation in many cases, and there have been many attempts to explain why this re-formulation has such an advantage. We try to explain the background mechanism of the BSSN equations by using eigenvalue analysis of constraint propagation equations. This analysis has been applied and has succeeded in explaining other systems in our series of works. We derive the full set of the constraint propagation equations, and study it in the flat background space-time. We carefully examine how the replacements and adjustments in the equations change the propagation structure of the constraints, i.e. whether violation of constraints (if it exists) will decay or propagate away. We conclude that the better stability of the BSSN system is obtained by their adjustments in the equations, and that the combination of the adjustments is in a good balance, i.e. a lack of their adjustments might fail to obtain the present stability. We further propose other adjustments to the equations, which may offer more stable features than the current BSSN equations.Comment: 10 pages, RevTeX4, added related discussion to gr-qc/0209106, the version to appear in Phys. Rev.

Case Report: An Unusual Case of Sudden Cardiovascular Collapse in an Elderly Adult

In our report we describe a case of foreign body aspiration leading to arrest. The patient’s resuscitation was remarkable for the development of a large pneumothorax and atelectasis of the right lung. Aspiration was suspected and early bronchoscopy was performed. A large grape was found to be obstructing the right main stem bronchus and was retrieved using a bronchoscopic snare. In this case early intervention allowed the removal of the intact grape with subsequent re-expansion of the lung. The technique used for retrieval is described

A trick for passing degenerate points in Ashtekar formulation

We examine one of the advantages of Ashtekar's formulation of general relativity: a tractability of degenerate points from the point of view of following the dynamics of classical spacetime. Assuming that all dynamical variables are finite, we conclude that an essential trick for such a continuous evolution is in complexifying variables. In order to restrict the complex region locally, we propose some `reality recovering' conditions on spacetime. Using a degenerate solution derived by pull-back technique, and integrating the dynamical equations numerically, we show that this idea works in an actual dynamical problem. We also discuss some features of these applications.Comment: 9 pages by RevTeX or 16 pages by LaTeX, 3 eps figures and epsf-style file are include

Sifat Dinamik Mekanikal Vulkanisat Karet Alam-organoclay

Sifat dinamik dan swelling vulkanisat karet alam (NR) yang mengandung bahan pengisi organoclay dengan basal spasi yang berbeda telah dipelajari. Vulkanisat NR/organoclay dibuat dengan menggunakan metode pelelehan kompon di dalam gilingan terbuka. Sifat dinamik diukur dengan menggunakan Dynamic Mechanical Thermal Analyzer (DMTA). Hasil penelitian menunjukkan bahwa penambahan organoclay dengan basal spasi lebih besar (15A) menghasilkan struktur interkalasi/eksfoliasi di dalam matrik karet alam sehingga sifat dinamik mekanikal dan swelling menjadi lebih baik. Storage modulus di bawah Tg dan di atas Tg meningkat dengan peningkatan basal spasi organoclay. Adanya organoclay juga menyebabkan penurunan tan d dan Tg vulkanisat, terutama organoclay 15A. Organoclay 15A di dalam vulkanisat karet alam dapat menurunkan nilai swelling dan koefisien difusi, sorptivitas serta permeabilitas. Derajat ikatan silang dari NR/organoclay 15A sedikit lebih besar dan memperbaiki sifat elastis vulkanisat. Diterima : 7 Januari 2013; Disetujui : 24 April 2013How to Cite : Faturrohman, M., Soegijono, B., Budianto, E., & Yoneda, K. (2013). Sifat Dinamik Mekanikal Vulkanisat Karet Alam-Organoclay. Jurnal Penelitian Karet, 31(1), 45-53. Retrieved from http://ejournal.puslitkaret.co.id/index.php/jpk/article/view/13

Geometrical optics analysis of the short-time stability properties of the Einstein evolution equations

Many alternative formulations of Einstein's evolution have lately been examined, in an effort to discover one which yields slow growth of constraint-violating errors. In this paper, rather than directly search for well-behaved formulations, we instead develop analytic tools to discover which formulations are particularly ill-behaved. Specifically, we examine the growth of approximate (geometric-optics) solutions, studied only in the future domain of dependence of the initial data slice (e.g. we study transients). By evaluating the amplification of transients a given formulation will produce, we may therefore eliminate from consideration the most pathological formulations (e.g. those with numerically-unacceptable amplification). This technique has the potential to provide surprisingly tight constraints on the set of formulations one can safely apply. To illustrate the application of these techniques to practical examples, we apply our technique to the 2-parameter family of evolution equations proposed by Kidder, Scheel, and Teukolsky, focusing in particular on flat space (in Rindler coordinates) and Schwarzchild (in Painleve-Gullstrand coordinates).Comment: Submitted to Phys. Rev.