7,207 research outputs found
MgII absorption systems with W_0 > 0.1 \AA for a radio selected sample of 77 QSOs and their associated magnetic fields at high redshifts
We present a catalogue of MgII absorption systems obtained from high
resolution UVES/VLT data of 77 QSOs in the redshift range 0.6 < z < 2.0, and
down to an equivalent width W_0 > 0.1 \AA. The statistical properties of our
sample are found to be in agreement with those from previous work in the
literature. However, we point out that the previously observed increase with
redshift of dN/dz for weak absorbers, pertains exclusively to very weak
absorbers with W_0 < 0.1 \AA. Instead, dN/dz for absorbers with W_0 in the
range 0.1-0.3 \AA actually decreases with redshift, similarly to the case of
strong absorbers. We then use this catalogue to extend our earlier analysis of
the links between the Faraday Rotation Measure of the quasars and the presence
of intervening MgII absorbing systems in their spectra. In contrast to the case
with strong MgII absorption systems W_0 > 0.3 \AA, the weaker systems do not
contribute significantly to the observed Rotation Measure of the background
quasars. This is possibly due to the higher impact parameters of the weak
systems compared to strong ones, suggesting that the high column density
magnetized material that is responsible for the Faraday Rotation is located
within about 50 kpc of the galaxies. Finally, we show that this result also
rules out the possibility that some unexpected secondary correlation between
the quasar redshift and its intrinsic Rotation Measure is responsible for the
association of high Rotation Measure and strong intervening MgII absorption
that we have presented elsewhere, since this would have produced an equal
effect for the weak absorption line systems, which exhibit a very similar
distribution of quasar redshifts.Comment: Accepted for publication in ApJ. 12 pages, 8 figure
The Kinematic Composition of MgII Absorbers
The study of galaxy evolution using quasar absorption lines requires an
understanding of what components of galaxies and their surroundings are
contributing to the absorption in various transitions. This paper considers the
kinematic composition of the class of 0.4 < z < 1.0 MgII absorbers,
particularly addressing the question of what fraction of this absorption is
produced in halos and what fraction arises from galaxy disks. We design models
with various fractional contributions from radial infall of halo material and
from a rotating thick disk component. We generate synthetic spectra from lines
of sight through model galaxies and compare the resulting ensembles of MgII
profiles with the 0.4 < z < 1.0 sample observed with HIRES/Keck. We apply a
battery of statistical tests and find that pure disk and pure halo models can
be ruled out, but that various models with rotating disk and infall/halo
contributions can produce an ensemble that is nearly consistent with the data.
A discrepancy in all models that we considered requires the existence of a
kinematic component intermediate between halo and thick disk. The variety of
MgII profiles can be explained by the gas in disks and halos of galaxies not
very much different than galaxies in the local Universe.
In any one case there is considerable ambiguity in diagnosing the kinematic
composition of an absorber from the low ionization high resolution spectra
alone. Future data will allow galaxy morphologies, impact parameters, and
orientations, FeII/MgII of clouds, and the distribution of high ionization gas
to be incorporated into the kinematic analysis. Combining all these data will
permit a more accurate diagnosis of the physical conditions along the line of
sight through the absorbing galaxy.Comment: 34 pages including 14 postscript figures; Accepted by the
Astrophysical Journal; URL http://www.astro.psu.edu/users/cwc/pubs.htm
Measuring Sustainability
Planning for sustainability is high on many agendas, and tools to measure sustainability have been developed. Sustainable processes are those whose rates are maintained over time without exceeding the innate ability of its surroundings to support the process. We present the necessary conditions along with a new algorithm for measuring the sustainability of processes that integrates the laws of thermodynamics with laws for rate processes. The algorithm permits the assessment of the degree of sustainability of any process, whether ecological, economic, or social, as well as chemical or biological. It is a dynamic approach that applies at any scale and takes into consideration the spatial and temporal factors of processes, thus permitting empirical applications that correspond to real world (dynamic, complex, evolving) conditions across space and time. These characteristics make it especially suitable for applications in the field of spatial planning
American Expatriates and the Building of Alternative Social Space in Toronto, 1965–1977
This article explores the history of U.S. expatriates and draft resisters in alternative political and cultural communities within Toronto during the late 1960s and early 1970s. As such these expatriates were important players in shaping and creating new social spaces, activist politics, and alternative forms of expression generated within the city’s counterculture communities and New Left movements. Aided by their class and racial privilege, many of these expatriates were able to participate in and engage the public culture of the city as few other migrants could. This ability to become part of the Toronto’s alternative neighbourhoods, scenes, and intentional communities was nonetheless facilitated by the transnational connections and objectives that linked local actions with global aspirations and collaborators.Cet article explore l’histoire des expatriés et insoumis américains dans les communautés politiques et culturelles alternatives de Toronto à la fin des années 60 et au début des années 70. Comme tels, ces expatriés ont été des acteurs importants dans l’élaboration et la création de nouveaux espaces sociaux, de la politique militante et d’autres formes d’expression issues du sein des communautés contre culturelles et des mouvements de la Nouvelle gauche. Aidés par la classe et le privilège racial, bon nombre de ces expatriés ont été en mesure de participer à la culture publique de la ville et de l’engager comme peu d’autres migrants. Cette capacité à intégrer les quartiers alternatifs de Toronto, ses scènes et ses communautés intentionnelles a néanmoins été facilitée par les connexions transnationales et les objectifs liant actions locales avec aspirations et collaborateurs mondiaux
An Ambiguous Welcome: Vietnam Draft Resistance, the Canadian State, and Cold War Containment
A significant portion of the growth in American immigration to Canada from the mid-
1960s to the mid-1970s was a consequence of the Vietnam War. For the Canadian
government, the appearance of large numbers of draft resisters at the border was a
boon. Draft resisters, if not deserters, tended to be young, middle-class, and educated
— the very type of immigrant the government wanted. Allowing entry to draft resisters
also reaped an important symbolic benefit in that it allowed the Canadian government
to demonstrate its independence from the United States and its opposition to the
war. In practice, however, not all young Americans resisting militarism were welcomed.
Government officials argued contradictory interpretations of the policy on
admitting draft resisters and deserters and their legal status in Canada. The Cold War
and the increased domestic concerns generated by student and protest movements in
the 1960s also solidified cooperation between the American and Canadian security
states in maintaining a surveillance of draft resisters and deserters.La guerre du Vietnam explique en bonne partie l’augmentation du nombre d’immigrants
américains franchissant la frontière canadienne du milieu des années 1960
jusqu’au milieu de la décennie suivante. Le gouvernement canadien s’est alors
réjoui de voir apparaître à ses portes de si nombreux dissidents. C’est que les
réfractaires à la conscription (s’agissant parfois même de déserteurs) étaient
généralement jeunes, de classe moyenne et instruits. Pour le gouvernement canadien,
il s’agissait là de l’immigrant idéal. Accueillir les réfractaires à la conscription
lui a aussi procuré un bienfait symbolique de taille, celui de marquer son
indépendance par rapport aux États-Unis et son opposition à la guerre. Mais dans
les faits, les jeunes Américains résistant au militarisme n’étaient pas tous les bienvenus.
Les fonctionnaires faisaient valoir des interprétations contradictoires de la
politique d’admission au Canada des réfractaires à l’appel sous les drapeaux et des
déserteurs et de leur statut juridique. Ajoutons à cela que la guerre froide et la multiplication
des préoccupations intérieures suscitées par les mouvements étudiants et
de protestation des années 1960 amenaient également les États américain et cana-
dien à collaborer plus étroitement sur le plan de la sécurité pour surveiller les
réfractaires et les déserteurs
Effect of pooling samples on the efficiency of comparative studies using microarrays
Many biomedical experiments are carried out by pooling individual biological
samples. However, pooling samples can potentially hide biological variance and
give false confidence concerning the data significance. In the context of
microarray experiments for detecting differentially expressed genes, recent
publications have addressed the problem of the efficiency of sample-pooling,
and some approximate formulas were provided for the power and sample size
calculations. It is desirable to have exact formulas for these calculations and
have the approximate results checked against the exact ones. We show that the
difference between the approximate and exact results can be large. In this
study, we have characterized quantitatively the effect of pooling samples on
the efficiency of microarray experiments for the detection of differential gene
expression between two classes. We present exact formulas for calculating the
power of microarray experimental designs involving sample pooling and technical
replications. The formulas can be used to determine the total numbers of arrays
and biological subjects required in an experiment to achieve the desired power
at a given significance level. The conditions under which pooled design becomes
preferable to non-pooled design can then be derived given the unit cost
associated with a microarray and that with a biological subject. This paper
thus serves to provide guidance on sample pooling and cost effectiveness. The
formulation in this paper is outlined in the context of performing microarray
comparative studies, but its applicability is not limited to microarray
experiments. It is also applicable to a wide range of biomedical comparative
studies where sample pooling may be involved.Comment: 8 pages, 1 figure, 2 tables; to appear in Bioinformatic
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