36 research outputs found
Post-Newtonian SPH calculations of binary neutron star coalescence. I. Method and first results
We present the first results from our Post-Newtonian (PN) Smoothed Particle
Hydrodynamics (SPH) code, which has been used to study the coalescence of
binary neutron star (NS) systems. The Lagrangian particle-based code
incorporates consistently all lowest-order (1PN) relativistic effects, as well
as gravitational radiation reaction, the lowest-order dissipative term in
general relativity. We test our code on sequences of single NS models of
varying compactness, and we discuss ways to make PN simulations more relevant
to realistic NS models. We also present a PN SPH relaxation procedure for
constructing equilibrium models of synchronized binaries, and we use these
equilibrium models as initial conditions for our dynamical calculations of
binary coalescence. Though unphysical, since tidal synchronization is not
expected in NS binaries, these initial conditions allow us to compare our PN
work with previous Newtonian results.
We compare calculations with and without 1PN effects, for NS with stiff
equations of state, modeled as polytropes with . We find that 1PN
effects can play a major role in the coalescence, accelerating the final
inspiral and causing a significant misalignment in the binary just prior to
final merging. In addition, the character of the gravitational wave signal is
altered dramatically, showing strong modulation of the exponentially decaying
waveform near the end of the merger. We also discuss briefly the implications
of our results for models of gamma-ray bursts at cosmological distances.Comment: RevTeX, 37 pages, 17 figures, to appear in Phys. Rev. D, minor
corrections onl
Antinociceptive activity of furan-containing congeners of improgan and ranitidine
Furan-containing congeners of the histamine H(2) receptor antagonist ranitidine were synthesized and tested for improgan-like antinociceptive activity. The most potent ligand of the series, VUF5498, is the most potent improgan-like agent described to date (ED(50)= 25 nmol, icv). This compound is approximately equal in potency with morphine. These non-imidazole, improgan-like pain relievers further define the structural requirements for analgesics of this class and are important tools for ongoing mechanism-based studies
Absence of antinociceptive tolerance to improgan, a cimetidine analog, in rats
Improgan, an analog of the histamine receptor antagonist cimetidine, produces highly effective analgesia following intraventricular injection. The present study examined changes in the antinociceptive effects of improgan following once daily intraventricular injections. Improgan (100-150 μg) produced near maximal antinociception 10 and 30 min after daily administration on all 4 test days, whereas comparable morphine treatments (50 μg) induced considerable tolerance. Thus, improgan produced highly effective analgesia without the development of tolerance