4,488 research outputs found
Expanding Our Boundaries With Information Literacy
Years ago I had a calling to a special ministry, but I didn\u27t think of it that way. At the time it seemed more a desire, whereas callings had to do with going into overseas missionary work or into a full time Christian ministry.
My calling came a few years after the birth of my son when I was working with a capital campaign for the United Presbyterian Church. The $50 million dollar campaign was coming to an end, and that meant my job would soon be over. Although I was offered a higher-level position with the Foundation - one I might add, which had only been held by men up until then, I kept thinking back to a black and white photograph and knew I had to become a librarian
Constraining Compact Object Formation with 2M0521
We show that the recently discovered binary 2M05215658+4359220 (2M0521),
comprised of a giant star (GS) orbiting a suspected black hole (BH) in a ~80
day orbit, may be instrumental in shedding light on uncertain BH-formation
physics and can be a test case for studying wind accretion models. Using binary
population synthesis with a realistic prescription for the star formation
history and metallicity evolution of the Milky Way, we analyze the evolution of
binaries containing compact objects (COs) in orbit around GSs with properties
similar to 2M0521. We find ~100-1000 CO-GS binaries in the Milky Way observable
by Gaia, and 0-12 BH-GS and 0-1 neutron star-GS binaries in the Milky Way with
properties similar to 2M0521. We find that all CO-GSs with Porb<5 yr, including
2M0521, go through a common envelope (CE) and hence form a class of higher mass
analogs to white dwarf post-CE binaries. We further show how the component
masses of 2M0521-like binaries depend strongly on the supernova-engine model we
adopt. Thus, an improved measurement of the orbit of 2M0521, imminent with
Gaia's third data release, will strongly constrain its component masses and as
a result inform supernova-engine models widely used in binary population
synthesis studies. These results have widespread implications for the origins
and properties of CO binaries, especially those detectable by LIGO and LISA.
Finally, we show that the reported X-ray non-detection of 2M0521 is a challenge
for wind accretion theory, making 2M0521-like CO-GS binaries a prime target for
further study with accretion models.Comment: 7 pages, 5 figures, Accepted for Publication in ApJ
The International Workshop on Wave Hindcasting and Forecasting and the Coastal Hazards Symposium
Following the 13th International Workshop on Wave Hindcasting and Forecasting
and 4th Coastal Hazards Symposium in October 2013 in Banff, Canada, a topical
collection has appeared in recent issues of Ocean Dynamics. Here we give a
brief overview of the history of the conference since its inception in 1986 and
of the progress made in the fields of wind-generated ocean waves and the
modelling of coastal hazards before we summarize the main results of the papers
that have appeared in the topical collection
The Leeway of Shipping Containers at Different Immersion Levels
The leeway of 20-foot containers in typical distress conditions is
established through field experiments in a Norwegian fjord and in open-ocean
conditions off the coast of France with wind speed ranging from calm to 14 m/s.
The experimental setup is described in detail and certain recommendations given
for experiments on objects of this size. The results are compared with the
leeway of a scaled-down container before the full set of measured leeway
characteristics are compared with a semi-analytical model of immersed
containers. Our results are broadly consistent with the semi-analytical model,
but the model is found to be sensitive to choice of drag coefficient and makes
no estimate of the cross-wind leeway of containers. We extend the results from
the semi-analytical immersion model by extrapolating the observed leeway
divergence and estimates of the experimental uncertainty to various realistic
immersion levels. The sensitivity of these leeway estimates at different
immersion levels are tested using a stochastic trajectory model. Search areas
are found to be sensitive to the exact immersion levels, the choice of drag
coefficient and somewhat less sensitive to the inclusion of leeway divergence.
We further compare the search areas thus found with a range of trajectories
estimated using the semi-analytical model with only perturbations to the
immersion level. We find that the search areas calculated without estimates of
crosswind leeway and its uncertainty will grossly underestimate the rate of
expansion of the search areas. We recommend that stochastic trajectory models
of container drift should account for these uncertainties by generating search
areas for different immersion levels and with the uncertainties in crosswind
and downwind leeway reported from our field experiments.Comment: 25 pages, 11 figures and 5 tables; Ocean Dynamics, Special Issue on
Advances in Search and Rescue at Sea (2012
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