638 research outputs found
Identifying clustering at high redshift through actively star-forming galaxies
Identifying galaxy clustering at high redshift (i.e. z > 1) is essential to
our understanding of the current cosmological model. However, at increasing
redshift, clusters evolve considerably in star-formation activity and so are
less likely to be identified using the widely-used red sequence method. Here we
assess the viability of instead identifying high redshift clustering using
actively star-forming galaxies (SMGs associated with over-densities of
BzKs/LBGs). We perform both a 2- and 3-D clustering analysis to determine
whether or not true (3D) clustering can be identified where only 2D data are
available. As expected, we find that 2D clustering signals are weak at best and
inferred results are method dependant. In our 3D analysis, we identify 12 SMGs
associated with an over-density of galaxies coincident both spatially and in
redshift - just 8% of SMGs with known redshifts in our sample. Where an SMG in
our target fields lacks a known redshift, their sightline is no more likely to
display clustering than blank sky fields; prior redshift information for the
SMG is required to identify a true clustering signal. We find that the strength
of clustering in the volume around typical SMGs, while identifiable, is not
exceptional. However, we identify a small number of highly clustered regions,
all associated with an SMG. The most notable of these, surrounding
LESSJ033336.8-274401, potentially contains an SMG, a QSO and 36 star-forming
galaxies (a > 20sig over-density) all at z~1.8. This region is highly likely to
represent an actively star-forming cluster and illustrates the success of using
star-forming galaxies to select sites of early clustering. Given the increasing
number of deep fields with large volumes of spectroscopy, or high quality and
reliable photometric redshifts, this opens a new avenue for cluster
identification in the young Universe.Comment: 24 pages, 14 figures, accepted MNRA
The Rest-Frame Submillimeter Spectrum of High-Redshift, Dusty, Star-Forming Galaxies
We present the average rest-frame spectrum of high-redshift dusty,
star-forming galaxies from 250-770GHz. This spectrum was constructed by
stacking ALMA 3mm spectra of 22 such sources discovered by the South Pole
Telescope and spanning z=2.0-5.7. In addition to multiple bright spectral
features of 12CO, [CI], and H2O, we also detect several faint transitions of
13CO, HCN, HNC, HCO+, and CN, and use the observed line strengths to
characterize the typical properties of the interstellar medium of these
high-redshift starburst galaxies. We find that the 13CO brightness in these
objects is comparable to that of the only other z>2 star-forming galaxy in
which 13CO has been observed. We show that the emission from the high-critical
density molecules HCN, HNC, HCO+, and CN is consistent with a warm, dense
medium with T_kin ~ 55K and n_H2 >~ 10^5.5 cm^-3. High molecular hydrogen
densities are required to reproduce the observed line ratios, and we
demonstrate that alternatives to purely collisional excitation are unlikely to
be significant for the bulk of these systems. We quantify the average emission
from several species with no individually detected transitions, and find
emission from the hydride CH and the linear molecule CCH for the first time at
high redshift, indicating that these molecules may be powerful probes of
interstellar chemistry in high-redshift systems. These observations represent
the first constraints on many molecular species with rest-frame transitions
from 0.4-1.2mm in star-forming systems at high redshift, and will be invaluable
in making effective use of ALMA in full science operations.Comment: 19 pages, 10 figures (2 in appendices); accepted for publication in
Ap
Extent of MGMT promoter methylation correlates with outcome in glioblastomas given temozolomide and radiotherapy
Urea and deuterium mixtures at high pressures
International audienceUrea, like many network forming compounds, has long been known to form inclusion (guest-host)compounds. Unlike other network formers like water, urea is not known to form such inclusioncompounds with simple molecules like hydrogen. Such compounds if they existed would be ofinterest both for the fundamental insight they provide into molecular bonding and as potential gasstorage systems. Urea has been proposed as a potential hydrogen storage material [T. A. Strobel et al.,Chem. Phys. Lett. 478, 97 (2009)]. Here, we report the results of high-pressure neutron diffractionstudies of urea and D2 mixtures that indicate no inclusion compound forms up to 3.7 GPa
Negotiating professional and social voices in research principles and practice
This paper draws on work conducted for a qualitative interview based study which explores the gendered racialised and professional identifications of health and social care professionals. Participants for the project were drawn from the professional executive committees of recently formed Primary Care Trusts. The paper discusses how the feminist psychosocial methodological approach developed for the project is theoretically, practically and ethically useful in exploring the voices of those in positions of relative power in relation to both health and social care services and the social relations of gender and ethnicity. The approach draws on psychodynamic accounts of (defended) subjectivity and the feminist work of Carol Gilligan on a voice-centred relational methodology. Coupling the feminist with the psychosocial facilitates an emphasis on voice and dialogic communication between participant and researcher not always captured in psychosocial approaches which tend towards favouring the interviewer as ‘good listener’. This emphasis on dialogue is important in research contexts where prior and ongoing relationships with professional participants make it difficult and indeed undesirable for researchers to maintain silence
Expression and trans-specific polymorphism of self-incompatibility RNases in Coffea (Rubiaceae)
Self-incompatibility (SI) is widespread in the angiosperms, but identifying the biochemical components of SI mechanisms has proven to be difficult in most lineages. Coffea (coffee; Rubiaceae) is a genus of old-world tropical understory trees in which the vast majority of diploid species utilize a mechanism of gametophytic self-incompatibility (GSI). The S-RNase GSI system was one of the first SI mechanisms to be biochemically characterized, and likely represents the ancestral Eudicot condition as evidenced by its functional characterization in both asterid (Solanaceae, Plantaginaceae) and rosid (Rosaceae) lineages. The S-RNase GSI mechanism employs the activity of class III RNase T2 proteins to terminate the growth of "self" pollen tubes. Here, we investigate the mechanism of Coffea GSI and specifically examine the potential for homology to S-RNase GSI by sequencing class III RNase T2 genes in populations of 14 African and Madagascan Coffea species and the closely related self-compatible species Psilanthus ebracteolatus. Phylogenetic analyses of these sequences aligned to a diverse sample of plant RNase T2 genes show that the Coffea genome contains at least three class III RNase T2 genes. Patterns of tissue-specific gene expression identify one of these RNase T2 genes as the putative Coffea S-RNase gene. We show that populations of SI Coffea are remarkably polymorphic for putative S-RNase alleles, and exhibit a persistent pattern of trans-specific polymorphism characteristic of all S-RNase genes previously isolated from GSI Eudicot lineages. We thus conclude that Coffea GSI is most likely homologous to the classic Eudicot S-RNase system, which was retained since the divergence of the Rubiaceae lineage from an ancient SI Eudicot ancestor, nearly 90 million years ago.United States National Science Foundation [0849186]; Society of Systematic Biologists; American Society of Plant Taxonomists; Duke University Graduate Schoolinfo:eu-repo/semantics/publishedVersio
Racism, anti-racist practice and social work: articulating the teaching and learning experiences of Black social workers
In the mid 1990s a Black practice teacher programme was established in Manchester and Merseyside with the primary aim to increase the number of Black practice teachers in social work organisations, and in turn provide a supportive and encouraging learning environment for Black student social workers whilst on placement. In the north‐west of England research has been undertaken, to establish the quality of the practice teaching and student learning taking place with Black practice teachers and students. This paper is an exploration of the ideas generated within the placement process that particularly focused on the discourse of racism and ant‐racist practice. Black students and practice teachers explain their understanding of racism and anti‐racist practice within social work. From the research, the paper will critique some of the ideas concerning anti‐racism. In particular, it will question whether anti‐racist social work practice needs to be re‐evaluated in the light of a context with new migrants, asylum seekers and refugees. It will concluded, by arguing that whilst the terms anti‐racism, Black and Minority Ethnic have resonance as a form of political strategic essentialism, it is important to develop more positive representations in the future
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