9,030 research outputs found
From Isotopes to TK Interviews: Towards Interdisciplinary Research in Fort Resolution and the Slave River Delta, Northwest Territories
Evolving research in Fort Resolution and the Slave River Delta, Northwest Territories, aims to improve understanding of how the natural ecosystem functions and responds to various environmental stressors, as well as to enhance the stewardship of natural resources and the capacity of local residents to respond to change. We seek to integrate approaches that span the natural and social sciences and traditional knowledge understandings of change, employing a research design developed in response to the concerns of a northern community. In doing so, we have strived for a research process that is collaborative, interdisciplinary, policy-oriented, and reflective of northern priorities. These elements characterize the new northern research paradigm increasingly promoted by various federal funding agencies, northern partners, and communities. They represent a holistic perspective in the pursuit of solutions to address complex environmental and socioeconomic concerns about impacts of climate change and resource development on northern societies. However, efforts to fulfill the objectives of this research paradigm are associated with a host of on-the-ground challenges. These challenges include (but are not restricted to) developing effective community partnerships and collaboration and documenting change through interdisciplinary approaches. Here we provide an overview of the components that comprise our interdisciplinary research program and offer an accounting of our formative experiences in confronting these challenges
Near-Infrared Properties of Moderate-Redshift Galaxy Clusters: Luminosity Functions and Density Profiles
We present K-band imaging for 15 of the Canadian Network for Observational
Cosmology (CNOC1) clusters. The cluster luminosity density and number density
profiles can be described by NFW models with concentration parameters of c_{l}
= 4.28 \pm 0.70 and c_{g} = 4.13 \pm 0.57 respectively. Comparing these to the
dynamical mass analysis of the same clusters shows that the galaxy luminosity
and number density profiles are similar to the dark matter profile, and are not
less concentrated like in local clusters. The luminosity functions show that
the evolution of K^{*} over the redshift range 0.2 < z < 0.5 is consistent with
a scenario where the majority of stars in cluster galaxies form at
high-redshift (z_{f} > 1.5) and evolve passively thereafter. The best-fit for
the faint-end slope of the luminosity function is alpha = -0.84 pm 0.08, which
indicates that it does not evolve between z = 0 and z = 0.3. Using Principal
Component Analysis of the spectra we classify cluster galaxies as either
star-forming/recently-star-forming (EM+BAL) or non-starforming (ELL) and
compute their respective luminosity functions. The faint-end slope of the ELL
luminosity function is much shallower than for the EM+BAL galaxies at z = 0.3,
and suggests the number of faint ELL galaxies in clusters decreases by a factor
of ~3 from z = 0 to z = 0.3. The redshift evolution of K^{*} for both EM+BAL
and ELL types is consistent with a passively evolving stellar population formed
at high-redshift. Passive evolution in both classes, as well as the total
cluster luminosity function, demonstrates that the bulk of the stellar
population in all bright cluster galaxies is formed at high-redshift and
subsequent transformations in morphology/color/spectral-type have little effect
on the total stellar mass.Comment: 22 pages, 16 figures, accepted by Ap
Suprachiasmatic Nucleus Neurons Are Glucose Sensitive
The suprachiasmatic nucleus (SCN) in the hypothalamus serves as the pacemaker for mammalian circadian rhythms. In a hamster brain slice preparation, the authors were able to record spontaneous activity from SCN cells for up to 4 days in vitro and verify a self-sustained rhythm in firing. The phase of this rhythm was altered by the concentration of glucose in the bathing medium, with time of peak firing advanced for a 20 mM glucose condition and slightly delayed for a 5 mM glucose condition, relative to 10 mM. The advancing effect of 20 mM glucose and the delaying effect of 5 mM glucose were not maintained during a 2nd day in vitro after changing the bathing medium back to 10 mM glucose, thus indicating the effect was not a permanent phase shift of the underlying oscillation. In experiments recording from cell-attached membrane patches on acutely dissociated hamster SCN neurons, exchanging the bathing medium from high (20 mM) to zero glucose increased potassium (K+)-selective channel activity. With inside-out membrane patches, the authors revealed the presence of a glybenclamide-sensitive K+ channel (190 pS) and a larger conductance (260 pS) Ca2+- dependent K+ channel that were both reversibly inhibited by ATP at the cytoplasmic surface. Furthermore, 1 mM tetraethylammonium chloride was demonstrated to advance peak firing time in the brain slice in a similar manner to a high concentration of glucose (20 mM). The authors interpret the results to imply that SCNs are sensitive to glucose, most probably via ATP modulation of K+ channel activity in these neurons. Tonic modulation of K+ channel activity appears to alter output of the pacemaker but does not reset the phase
Pancreatic Exocrine Insufficiency and the Gut Microbiome in Pancreatic Cancer:A Target for Future Diagnostic Tests and Therapies?
From Isotopes to TK Interviews: Towards Interdisciplinary Research in Fort Resolution and the Slave River Delta, Northwest Territories
Evolving research in Fort Resolution and the Slave River Delta, Northwest Territories, aims to improve understanding of how the natural ecosystem functions and responds to various environmental stressors, as well as to enhance the stewardship of natural resources and the capacity of local residents to respond to change. We seek to integrate approaches that span the natural and social sciences and traditional knowledge understandings of change, employing a research design developed in response to the concerns of a northern community. In doing so, we have strived for a research process that is collaborative, interdisciplinary, policy-oriented, and reflective of northern priorities. These elements characterize the new northern research paradigm increasingly promoted by various federal funding agencies, northern partners, and communities. They represent a holistic perspective in the pursuit of solutions to address complex environmental and socioeconomic concerns about impacts of climate change and resource development on northern societies. However, efforts to fulfill the objectives of this research paradigm are associated with a host of on-the-ground challenges. These challenges include (but are not restricted to) developing effective community partnerships and collaboration and documenting change through interdisciplinary approaches. Here we provide an overview of the components that comprise our interdisciplinary research program and offer an accounting of our formative experiences in confronting these challenges.Des travaux de recherche en cours à Fort Resolution et dans le delta de la rivière des Esclaves, aux Territoires du Nord-Ouest, visent à mieux comprendre le fonctionnement de l’écosystème naturel, à réagir aux divers facteurs d’agression environnementaux ainsi qu’à rehausser la gérance des ressources naturelles et la capacité des habitants de la région à réagir au changement. Nous cherchons à intégrer des méthodes qui englobent les sciences naturelles et sociales et favorisent la compréhension du changement du point de vue des connaissances traditionnelles. Nous cherchons également à employer une méthodologie respectueuse des inquiétudes de la collectivité du Nord. Ce faisant, nous avons abouti à un processus de recherche caractérisé par la collaboration, l’interdisciplinarité et les politiques, processus qui tient également compte des priorités dans le Nord. Ces éléments définissent le nouveau paradigme de recherche dans le Nord qui est de plus en plus préconisé par divers organismes de subvention fédéraux, partenaires du Nord et collectivités. Ils représentent une perspective holistique en guise de solutions à des enjeux environnementaux et socioéconomiques complexes portant sur les incidences du changement climatique et de l’exploitation des ressources sur les sociétés du Nord. Toutefois, les efforts visant à concrétiser les objectifs de ce paradigme de recherche font face à une multitude de défis. Ces défis comprennent (mais sans s’y restreindre) la formation de partenariats efficaces avec les collectivités, des efforts de collaboration et la prise de notes sur les changements qui s’opèrent grâce à des méthodes interdisciplinaires. Ici, nous fournissons un aperçu des éléments de notre programme de recherche interdisciplinaire et donnons un aperçu de l’expérience formative qui a découlé de ces défis
Spectroscopic Target Selection in the Sloan Digital Sky Survey: The Quasar Sample
We describe the algorithm for selecting quasar candidates for optical
spectroscopy in the Sloan Digital Sky Survey. Quasar candidates are selected
via their non-stellar colors in "ugriz" broad-band photometry, and by matching
unresolved sources to the FIRST radio catalogs. The automated algorithm is
sensitive to quasars at all redshifts lower than z=5.8. Extended sources are
also targeted as low-redshift quasar candidates in order to investigate the
evolution of Active Galactic Nuclei (AGN) at the faint end of the luminosity
function. Nearly 95% of previously known quasars are recovered (based on 1540
quasars in 446 square degrees). The overall completeness, estimated from
simulated quasars, is expected to be over 90%, whereas the overall efficiency
(quasars:quasar candidates) is better than 65%. The selection algorithm targets
ultraviolet excess quasars to i^*=19.1 and higher-redshift (z>3) quasars to
i^*=20.2, yielding approximately 18 candidates per square degree. In addition
to selecting ``normal'' quasars, the design of the algorithm makes it sensitive
to atypical AGN such as Broad Absorption Line quasars and heavily reddened
quasars.Comment: 62 pages, 15 figures (8 color), 8 tables. Accepted by AJ. For a
version with higher quality color figures, see
http://archive.stsci.edu/sdss/quasartarget/RichardsGT_qsotarget.preprint.p
The Green Bank Ammonia Survey (GAS): First Results of NH3 mapping the Gould Belt
We present an overview of the first data release (DR1) and first-look science
from the Green Bank Ammonia Survey (GAS). GAS is a Large Program at the Green
Bank Telescope to map all Gould Belt star-forming regions with
mag visible from the northern hemisphere in emission from NH and other key
molecular tracers. This first release includes the data for four regions in
Gould Belt clouds: B18 in Taurus, NGC 1333 in Perseus, L1688 in Ophiuchus, and
Orion A North in Orion. We compare the NH emission to dust continuum
emission from Herschel, and find that the two tracers correspond closely.
NH is present in over 60\% of lines-of-sight with mag in
three of the four DR1 regions, in agreement with expectations from previous
observations. The sole exception is B18, where NH is detected toward ~ 40\%
of lines-of-sight with mag. Moreover, we find that the NH
emission is generally extended beyond the typical 0.1 pc length scales of dense
cores. We produce maps of the gas kinematics, temperature, and NH column
densities through forward modeling of the hyperfine structure of the NH
(1,1) and (2,2) lines. We show that the NH velocity dispersion,
, and gas kinetic temperature, , vary systematically between
the regions included in this release, with an increase in both the mean value
and spread of and with increasing star formation activity.
The data presented in this paper are publicly available.Comment: 33 pages, 27 figures, accepted to ApJS. Datasets are publicly
available: https://dataverse.harvard.edu/dataverse/GAS_DR
- …