6,980 research outputs found
HEAO-A nominal scanning observation schedule
The HEAO-A observatory, scheduled for launch in late June 1977, will spend most of its orbital lifetime in a scanning mode, spining from 0.03 to 0.1 rpm about an axis aligned with the sun. The dates of availability in the scan band are given for a list of 248 X-ray sources. Celestial maps of source locations and scan planes, and examples of the nighttime elevation of available sources are presented. This document is intended to aid ground-based observers in planning coordinated observations with HEAO-A
Semiclassical Accuracy in Phase Space for Regular and Chaotic Dynamics
A phase-space semiclassical approximation valid to at short times
is used to compare semiclassical accuracy for long-time and stationary
observables in chaotic, stable, and mixed systems. Given the same level of
semiclassical accuracy for the short time behavior, the squared semiclassical
error in the chaotic system grows linearly in time, in contrast with quadratic
growth in the classically stable system. In the chaotic system, the relative
squared error at the Heisenberg time scales linearly with ,
allowing for unambiguous semiclassical determination of the eigenvalues and
wave functions in the high-energy limit, while in the stable case the
eigenvalue error always remains of the order of a mean level spacing. For a
mixed classical phase space, eigenvalues associated with the chaotic sea can be
semiclassically computed with greater accuracy than the ones associated with
stable islands.Comment: 9 pages, 6 figures; to appear in Physical Review
Extent and mechanism of sealing in transected giant axons of squid and earthworms
Transected axons are often assumed to seal at their cut
ends by the formation of continuous membrane barriers that
allow for the restoration of function in the axonal stumps.
We have used several electrophysiological measures (membrane
potential, input resistance, injury current density) and
several morphological measures (phase-contrast, video-enhanced
differential interference contrast, light, and electron
microscopies) of living and fixed material to assess the extent
and mechanism of sealing within hours after transecting
giant axons of squid (Loligo pealeiand Sepioteuthis lessoniana)
and earthworms (Lumbricus terrestris). Our electrophysiological
data suggest that the proximal and distal ends
of transected squid giant axons do not completely seal within
2.5 hr in physiological saline. In contrast, the same set of
measures suggest that proximal and distal ends of transected
earthworm giant axons seal within 1 hr in physiological
saline. Our morphological data show that the cut ends
of both squid and earthworm axons constrict, but that a 20-
70-am-diameter opening always remains at the cut end that
is filled with vesicles. Axonal transection induces the formation
of vesicles that are observed in the axoplasm within
minutes in standard salines and that rapidly migrate to the
cut ends. These injury-induced vesicles are loosely packed
near the cut ends of squid giant axons, which do not functionally
seal within 2.5 hr of transection. In contrast, vesicles
formed a tightly packed plug at the cut ends of earthworm
medial giant axons, which do functionally seal within 1 hr of
transection in physiological saline. Since we detect no single
continuous membrane that spans the cut end, sealing does
not appear to occur by the fusion of constricted axolemmal
membrane or the formation of a membranous partition at the
cut end. Rather, our data are consistent with the hypothesis
that a tightly packed vesicular plug is responsible for sealing
of earthworm giant axons.This work was supported in part by NIH Grant NS31256 and ONR Grant N00014-90-J-1137 to H.M.F., an NIAAA fellowship to T.L.K., and an ATP grant to G.D.B.Neuroscienc
Scaling Properties of Weak Chaos in Nonlinear Disordered Lattices
The Discrete Nonlinear Schroedinger Equation with a random potential in one
dimension is studied as a dynamical system. It is characterized by the length,
the strength of the random potential and by the field density that determines
the effect of nonlinearity. The probability of the system to be regular is
established numerically and found to be a scaling function. This property is
used to calculate the asymptotic properties of the system in regimes beyond our
computational power.Comment: 4 pages, 5 figure
Property Rights, Reliance, and Retroactivity Under the Communications Act of 1934
Although the FCC and courts have concluded that licensees have certain property interests in their licenses, they do not acquire any ownership interests even when, via a spectrum auction, they pay for their licenses. What narrow property interests licensees maintain are limited, and the FCC has broad power to modify existing licenses if doing so is in the public interest. License owners have sought to limit or defeat otherwise lawful FCC actions to alter their licenses by asserting a reliance interest on prior agency action or policy. Licensees may find comfort in the fact that some courts have acknowledged these claims, and have determined that the FCC, at a minimum, must treat licensees equitably. It is proposed that, even in the absence of traditional property rights, such claims be available to facilitate careful judicial review of FCC action
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