29,449 research outputs found
A computerized program for statistical treatment of biological data
Biologists frequently conduct experiments which measure the patterns of inactivation of bacterial populations after exposure to a lethal environment. A computer program is discussed which calculates many of the quantities that have proven to be useful in the analysis of such experimental data
Energetic Impact of Jet Inflated Cocoons in Relaxed Galaxy Clusters
Jets from active galactic nuclei (AGN) in the cores of galaxy clusters have
the potential to be a major contributor to the energy budget of the
intracluster medium (ICM). To study the dependence of the interaction between
the AGN jets and the ICM on the parameters of the jets themselves, we present a
parameter survey of two-dimensional (axisymmetric) ideal hydrodynamic models of
back-to-back jets injected into a cluster atmosphere (with varying Mach numbers
and kinetic luminosities). We follow the passive evolution of the resulting
structures for several times longer than the active lifetime of the jet. The
simulations fall into roughly two classes, cocoon-bounded and non-cocoon
bounded sources. We suggest a correspondence between these two classes and the
Faranoff-Riley types. We find that the cocoon-bounded sources inject
significantly more entropy into the core regions of the ICM atmosphere, even
though the efficiency with which energy is thermalized is independent of the
morphological class. In all cases, a large fraction (50--80%) of the energy
injected by the jet ends up as gravitational potential energy due to the
expansion of the atmosphere.Comment: 12 pages, Accepted for publication in Ap
NuSTAR Observations of G11.2–0.3
We present in this paper the hard X-ray view of the pulsar wind nebula in G11.2−0.3 and its central pulsar powered pulsar J1811−1925 as seen by NuSTAR. We complement the data with Chandra for a more complete picture and confirm the existence of a hard, power-law component in the shell with photon index Γ = 2.1 ± 0.1, which we attribute to synchrotron emission. Our imaging observations of the shell show a slightly smaller radius at higher energies, consistent with Chandra results, and we find shrinkage as a function of increased energy along the jet direction, indicating that the electron outflow in the PWN may be simpler than that seen in other young PWNe. Combining NuSTAR with INTEGRAL, we find that the pulsar spectrum can be fit by a power law with Γ = 1.32 ± 0.07 up to 300 keV without evidence of curvature
Observations of the Extended Distribution of Ionized Hydrogen in the Plane of M31
We have used the Wisconsin H-Alpha Mapper (WHAM) to observe the spatially
extended distribution of ionized hydrogen in M31 beyond the stellar disk. We
obtained five sets of observations, centered near the photometric major axis of
M31, that extend from the center of the galaxy to just off the edge of the
southwestern HI disk. Beyond the bright stellar disk, but within the HI disk,
weak H-alpha is detected with an intensity I(H-alpha) = 0.05 (+0.01 / -0.02)
Rayleighs. Since M31 is inclined 77 degrees with respect to the line of sight,
this implies that the ambient intergalactic ionizing flux onto each side of M31
is Phi_0 <= 1.6 x 10^4 photons cm^-2 s^-1. Just beyond the outer boundary of
the HI disk we find no significant detection of H-alpha and place an upper
limit I(H-alpha) <= 0.019 Rayleighs.Comment: To appear in ApJ Letters; 12 pages, 4 figure
Who Owned Waterloo? Wellington’s Veterans and the Battle for Relevance
This dissertation examines the afterlife of the battle of Waterloo in the collective memory of Great Britain as well as the post-war lives of officers who fought there. Using a variety of techniques associated with cultural, social, and military history, it explores the concept of cultural ownership of a military event and contextualizes the relationship between Britain and her army in the nineteenth century, both at home and abroad. It argues that, almost immediately after the dust settled on the field of Waterloo, a variety of groups laid claim to different aspects of the ownership of the memory of the battle within Great Britain, resulting in a nationalization of the victory that was often complex and marked by overlapping claims. Over the thirty-seven years between the battle in 1815 and the Duke of Wellington’s funeral in 1852, those groups employed histories, memoirs, patronage, tourism, relic collecting, annual commemorations, performances, social interactions, and a variety of art and literature to celebrate Britain’s victory, further craft and delineate their own identities, and incorporate the battle into the wider creation myth of Great Britain.
To best explore Britain’s relationship with its army and with the victory at Waterloo, this dissertation is divided into two sections, the first comprising four chapters and the second three. The first section charts the cultural history of the British officer corps and the collective memory of the Battle of Waterloo, allowing for a detailed exploration of the question of ownership of a military victory, both within Britain and internationally. The first chapter contrasts military memoirs with civilian histories. The second examines Waterloo itself as a pilgrimage destination, while widening the question of ownership to include physical items and monuments. The third discusses military and civilian commemorations and celebrations of the Battle of Waterloo, from 1815 until the 1850s. The concluding chapter explores depictions of officers in the popular culture and media of the day. The second section begins with a chapter on the army at home (including Ireland), which discusses the change from wartime to peacetime service. The second chapter examines the involvement of officers in politics, focusing on veterans who followed Wellington’s lead and entered parliament. The third chapter covers veterans appointed by London to positions in the imperial service. The dissertation concludes with an epilogue on Wellington’s state funeral in 1852, arguing that this event served as the culmination of many of the cultural and social trends discussed throughout the work
Properties of AGN coronae in the NuSTAR era
The focussing optics of NuSTAR have enabled high signal-to-noise spectra to
be obtained from many X-ray bright Active Galactic Nuclei (AGN) and Galactic
Black Hole Binaries (BHB). Spectral modelling then allows robust
characterization of the spectral index and upper energy cutoff of the coronal
power-law continuum, after accounting for reflection and absorption effects.
Spectral-timing studies, such as reverberation and broad iron line fitting, of
these sources yield coronal sizes, often showing them to be small and in the
range of 3 to 10 gravitational radii in size. Our results indicate that coronae
are hot and radiatively compact, lying close to the boundary of the region in
the compactness - temperature diagram which is forbidden due to runaway pair
production. The coincidence suggests that pair production and annihilation are
essential ingredients in the coronae of AGN and BHB and that they control the
shape of the observed spectra.Comment: 11 pages, 8 figures, accepted for publication in MNRA
Compositional nanodomain formation in hybrid formate perovskites
We report the synthesis and structural characterisation of three mixed-metal
formate perovskite families [C(NH)]MCu(HCOO) (M = Mn,
Zn, Mg). Using a combination of infrared spectroscopy, non-negative matrix
factorization, and reverse Monte Carlo refinement, we show that the Mn- and
Zn-containing compounds support compositional nanodomains resembling the polar
nanoregions of conventional relaxor ferroelectrics. The M = Mg family exhibits
a miscibility gap that we suggest reflects the limiting behaviour of nanodomain
formation.Comment: 4 pages, 3 figure
Recommended from our members
Consulting the Experts
Alan Simpson and Lisa Reynolds outline how mental health nursing students learned about users’ experiences through an innovative e-learning projec
- …