1,110 research outputs found
An explicit harmonic code for black-hole evolution using excision
We describe an explicit in time, finite-difference code designed to simulate black holes by using the excision method. The code is based upon the harmonic formulation of the Einstein equations and incorporates several features regarding the well-posedness and numerical stability of the initial-boundary problem for the quasilinear wave equation. After a discussion of the equations solved and of the techniques employed, we present a series of testbeds carried out to validate the code. Such tests range from the evolution of isolated black holes to the head-on collision of two black holes and then to a binary black hole inspiral and merger. Besides assessing the accuracy of the code, the inspiral and merger test has revealed that individual apparent horizons can touch and even intersect. This novel feature in the dynamics of the marginally trapped surfaces is unexpected but consistent with theorems on the properties of apparent horizons
COMPARATIVE ANALYSIS OF THE CHANGES OF THE MASS MOMENTS OF INERTIA DURING A BREAST-STROKE
A new method of investigation of athletes' motion takes into consideration the changes of the principal moments of inertia and their directions during the interval of the motion, because these characterise the efficiency and the neuro-muscular regulation of the motion. This paper presents a comparative analysis of two top swimmers (Swl=Rozsa, Sw2=Guttler) and points out the significant difference caused by their alternate motion pattern
Comparative in vitro studies on native and recombinant human cationic trypsins - Cathepsin B is a possible pathological activator of trypsinogen in pancreatitis
Hereditary pancreatitis, an autosomal dominant disease is
believed to
be caused by mutation in the human trypsinogen gene. The role of
mutations has been investigated by in vitro studies using
recombinant
rat and human trypsinogen (TG), In this study we compare the
enzymatic
properties and inhibition by human pancreatic secretory trypsin
inhibitor (hPSTI) of the native, postsynthetically modified and
recombinant cationic trypsin, and found these values practically
identical, We also determined the autolytic stability of
recombinant
wild type (Hu1Asn21) and pancreatitis-associated (Hu1Ile21)
trypsin,
Both forms were equally stable. Similarly, we found no
difference in
the rate of activation of the two zymogens by human cationic and
anionic trypsin. Mesotrypsin did not activate either form. The
rate of
autocatalytic activation of Hu1Asn21 TG and Hu1Ile21 TG was also
identical at pH 8 both in the presence and absence of Ca2+. At
pH 5
Hu1Ile21 TG autoactivated about twice as fast as HulAsn21 TG,
The
presence of physiological amount of hPSTI completely prevented
autoactivation of both zymogens at pH 8 and at pH 5 as well.
Cathepsin
B readily activated both zymogens although Hu1Ile21 TG was
activated
about 2.5-3 times as fast as Hu1Asn21 TG, The presence of hPSTI
did not
prevent the activation of zymogens by cathepsin B, Our results
underlie
the central role of cathepsin B in the development of different
forms
of pancreatitis
KINEMATIC ANALYSIS OF SURFACE AND UNDERWATER FIN-SWIMMING
The aim of the study was to perform a comparative kinematic analysis of surface and underwater fin-swimming. Results of the experiments were obtained in terms of motion as well as maximum and minimum differences between the technique of surface and underwater fin-swimming
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.
Improving Post-Operative Outcomes in Aged and Diabetic Obese Mice
Due to their small size, high metabolic rate, and large surface to volume ratio, mice are a challenge to work with surgically and peri-operatively. Working with mice that are more susceptible to anesthetic agents, aged, or obese (e.g., diabetic mice), provides even more challenges. In two separate studies, we found simple that supportive care measures during and after surgery improved post-operative outcomes
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