2,792 research outputs found
Generation X leaders from London, New York and Toronto
Inspired by scholarly calls to focus more intently on the influence of context on leadersâ construction and negotiation of identity, this paper draws on evidence from our Economic and Social Research Council (ESRC) project in London, New York City and Toronto. Throughout the paper, we strive to illuminate how the city-based context influences how race/ethnicity is experienced and described. We use social identity theory, organisational fit and in-group prototypes to frame school leadersâ explicit discuss race/ethnicity when reflecting on identity. We describe our data gathering process using our Professional Identity card-sort Tool, which guided leadersâ reflections on identity. The analysis details how we extracted and interpreted evidence from leaders who were explicit about the interrelationship between their own personal racial/ethnic identification and its alignment or misalignment with their school-level communities. We explore how different city contexts influence leader experience of in-groups and out-groups and the related leadership challenges and opportunities. In conclusion, we reflect on the influence that structures, policies and communities have on how leaders experience identity and the possible implications for their work. We also explore the value of attending to potential context-based identity-driven experiences for school leader development and support
A Differential X-Ray Gunn-Peterson Test Using a Giant Cluster Filament
Using CCD detectors onboard the forthcoming X-ray observatories Chandra and
XMM, it is possible to devise a measurement of the absolute density of heavy
elements in the hypothetical warm gas filling intercluster space. This gas may
be the largest reservoir of baryonic matter in the Universe, but even its
existence has not been proven observationally at low redshifts. The proposed
measurement would make use of a unique filament of galaxy clusters spanning
over 700 Mpc (0.1<z<0.2) along the line of sight in a small area of the sky in
Aquarius. The surface density of Abell clusters there is more than 6 times the
sky average. It is likely that the intercluster matter column density is
enhanced by a similar factor, making its detection feasible under certain
optimistic assumptions about its density and elemental abundances. One can
compare photoabsorption depth, mostly in the partially ionized oxygen edges, in
the spectra of clusters at different distances along the filament, looking for
a systematic increase of depth with the distance. The absorption can be
measured by the same detector and through the same Galactic column, hence the
differential test. A CCD moderate energy resolution (about 100 eV) is adequate
for detecting an absorption edge at a known redshift.Comment: Latex, 4 pages, 3 figures, uses emulateapj.sty. ApJ Letters in pres
Majorana fermions emerging from magnetic nanoparticles on a superconductor without spin-orbit coupling
There exists a variety of proposals to transform a conventional s-wave
superconductor into a topological superconductor, supporting Majorana fermion
mid-gap states. A necessary ingredient of these proposals is strong spin-orbit
coupling. Here we propose an alternative system consisting of a one-dimensional
chain of magnetic nanoparticles on a superconducting substrate. No spin-orbit
coupling in the superconductor is needed. We calculate the topological quantum
number of a chain of finite length, including the competing effects of disorder
in the orientation of the magnetic moments and in the hopping energies, to
identify the transition into the topologically nontrivial state (with Majorana
fermions at the end points of the chain).Comment: 7 pages, 5 figure
X-ray Properties of the Abell 644 Cluster of Galaxies
We use new ASCA observations and archival ROSAT Position Sensitive
Proportional Counter (PSPC) data to determine the X-ray spectral properties of
the intracluster gas in Abell 644. From the overall spectrum, we determine the
average gas temperature to be 8.64 (+0.67,-0.56) keV, and an abundance of 0.32
(+/-0.04) . The global ASCA and ROSAT spectra imply a cooling rate
of 214 (+100,-91) yr. The PSPC X-ray surface brightness
profile and the ASCA data suggest a somewhat higher cooling rate. We determine
the gravitational mass and gas mass as a function of radius. The total
gravitating mass within 1.2 Mpc is , of which 20%
is in the form of hot gas. There is a region of elevated temperature 1.5-5
arcmin to the west of the cluster center. The south-southwest region of the
cluster also shows excess emission in the ROSAT PSPC X-ray image, aligned with
the major axis of the optical cD galaxy in the center of the cluster. We argue
that the cluster is undergoing or has recently undergone a minor merger. The
combination of a fairly strong cooling flow and evidence for a merger make this
cluster an interesting case to test the disruption of cooling flow in mergers.Comment: 26 pages LaTeX including 9 eps figures + 4 pages LaTeX tables
(landscape); accepted to ApJ, uses aaspp
An infrared survey of brightest cluster galaxies: Paper I
We report on an imaging survey with the Spitzer Space Telescope of 62
brightest cluster galaxies with optical line emission. These galaxies are
located in the cores of X-ray luminous clusters selected from the ROSAT All-Sky
Survey. We find that about half of these sources have a sign of excess infrared
emission; 22 objects out of 62 are detected at 70 microns, 18 have 8 to 5.8
micron flux ratios above 1.0 and 28 have 24 to 8 micron flux ratios above 1.0.
Altogether 35 of 62 objects in our survey exhibit at least one of these signs
of infrared excess. Four galaxies with infrared excesses have a 4.5/3.6 micron
flux ratio indicating the presence of hot dust, and/or an unresolved nucleus at
8 microns. Three of these have high measured [OIII](5007A)/Hbeta flux ratios
suggesting that these four, Abell 1068, Abell 2146, and Zwicky 2089, and
R0821+07, host dusty active galactic nuclei (AGNs). 9 objects (including the
four hosting dusty AGNs) have infrared luminosities greater than 10^11 L_sol
and so can be classified as luminous infrared galaxies (LIRGs). Excluding the
four systems hosting dusty AGNs, the excess mid-infrared emission in the
remaining brightest cluster galaxies is likely related to star formation.Comment: accepted for publication in ApJ
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