88,613 research outputs found
Managing Uncertainty: Lessons from Xenophon\u27s Retreat
Propositions on dynamic capabilities and organizational politics are developed from management literature and are then evaluated using case analysis. The goal is to identify complementary aspects of these perspectives to change from an ancient example that can offer insights for management thought and practice today. Initially chronicled by Xenophon, roughly 10,000 Greek mercenaries spent over two years confronting demanding circumstances as they fought their way into and out of ancient Persia. The mercenaries\u27 response to changing circumstances offers a unique case for integrating literature on responses to uncertainty that range between rational and haphazard explanations. The analysis suggests uncertainty management is a complex phenomenon imperfectly represented by existing models
Black-Hole Transients and the Eddington Limit
I show that the Eddington limit implies a critical orbital period P_crit(BH)
= 2d beyond which black-hole LMXBs cannot appear as persistent systems. The
unusual behaviour of GRO J1655-40 may result from its location close to this
critical period.Comment: 3 pages, no figures; to appear in MNRA
The American Aircraft Industrial Base: On the Brink
An article reviewing the decline in the American aircraft industrial base
Ultraluminous X-ray Sources and Star Formation
Chandra observations of the Cartwheel galaxy reveal a population of
ultraluminous X-ray sources (ULXs) with lifetimes < 10^7 yr associated with a
spreading wave of star formation which began some 3 x 10^8 yr ago. A population
of high-mass X-ray binaries provides a simple model: donor stars of initial
masses M_2 > 15 Msun transfer mass on their thermal timescales to black holes
of masses M_1 > 10 Msun.
For alternative explanations of the Cartwheel ULX population in terms of
intermediate-mass black holes (IMBH) accreting from massive stars, the inferred
production rate > 10^-6 yr^-1 implies at least 300 IMBHs, and more probably 3 x
10^4, within the star-forming ring. These estimates are increased by factors
eta^-1 if the efficiency eta with which IMBHs find companions of > 15 Msun
within 10^7 yr is <1. Current models of IMBH production would require a very
large mass (\ga 10^{10}\msun) of stars to have formed new clusters. Further,
the accretion efficiency must be low (< 6 x 10^-3) for IMBH binaries,
suggesting super-Eddington accretion, even though intermediate black hole
masses are invoked with the purpose of avoiding it.
These arguments suggest either that to make a ULX, an IMBH must accrete from
some as yet unknown non-stellar mass reservoir with very specific properties,
or that most if not all ULXs in star-forming galaxies are high-mass X-ray
binaries.Comment: 3 pages, no figures; MNRAS accepted with minor amendment
Balanced Innovation Management
The Department of Defense has demonstrated success in managing innovation. The military’s approach to innovation management extends beyond traditional distinctions between internal and external innovation modes. Summarizing specific innovation strategies available to managers develops recognition of this growing reality. The article concludes with resulting lessons that can be more widely adopted by managers
Improved high volume air sampler
Sampler permits size separations of particles by directing sampled air through cross-sectional area sufficiently large that air velocity is reduced to point where particles or larger size will settle out. Sampler conducts air downward and through slots around periphery of unit into relatively open interior of house
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