1,987 research outputs found
Collective Survival Strategies and Anti-Colonial Practice in Ecosocial Work
Oppressed communities have long used strategies of caring for and protecting each other to ensure their collective survival. We argue for ecosocial workers to critically interrogate how agency, history, and culture structure environmental problems and our responses to them, by developing a resilience-based framework, collective survival strategies (CSS). CSS consider power, culture and history and build upon the strengths of oppressed communities facing global environmental changes. We challenge the dominant narrative of climate change as a “new” problem and connect it to colonization. We discuss implications by examining a social work program explicitly built on Indigenous knowledges and anti-colonial practice
A high-throughput qPCR system for simultaneous quantitative detection of dairy <em>Lactococcus lactis</em> and <em>Leuconostoc</em> bacteriophages
Simultaneous quantitative detection of Lactococcus (Lc.) lactis and Leuconostoc species bacteriophages (phages) has not been reported in dairies using undefined mixed-strain DL-starters, probably due to the lack of applicable methods. We optimized a high-throughput qPCR system that allows simultaneous quantitative detection of Lc. lactis 936 (now SK1virus), P335, c2 (now C2virus) and Leuconostoc phage groups. Component assays are designed to have high efficiencies and nearly the same dynamic detection ranges, i.e., from ~1.1 x 105 to ~1.1 x 101 phage genomes per reaction, which corresponds to ~9 x 107 to ~9 x 103 phage particles mL-1 without any additional up-concentrating steps. The amplification efficiencies of the corresponding assays were 100.1±2.6, 98.7±2.3, 101.0±2.3 and 96.2±6.2. The qPCR system was tested on samples obtained from a dairy plant that employed traditional mother-bulk-cheese vat system. High levels of 936 and P335 phages were detected in the mother culture and the bulk starter, but also in the whey samples. Low levels of phages were detected in the cheese milk samples
'Let's see if it won't go away by itself.' LGBT microaggressions among teachers in South Africa
We explored types and qualities of microaggressions or subtle forms of discrimination towards lesbian, gay, bisexual and transgender (LGBT) people among teachers in South Africa. For data collection, we used in-depth interviews. Twenty-five Life Orientation teachers, nine men and 16 women, from both rural and urban schools throughout the Free State Province participated. Our findings suggest heterosexism as well as subtle and sometimes harder to pin down forms of bias – microaggressions ‒ are experienced in these contexts. Given the educational policy shifts on LGBT rights in South Africa, we argue that microaggressions need to be clearly located in the larger macro context of systemic heterosexism which pervades schools and the teaching of sexuality education in South Africa. We conclude with implications for teaching and support interventions to make schools more LGBT inclusive.</p
Preprocessing Among the Infalling Galaxy Population of EDisCS Clusters
We present results from a low-resolution spectroscopic survey for 21 galaxy
clusters at selected from the ESO Distant Cluster Survey. We
measured spectra using the low-dispersion prism in IMACS on the Magellan Baade
telescope and calculate redshifts with an accuracy of . We
find 1763 galaxies that are brighter than in the large-scale cluster
environs. We identify the galaxies expected to be accreted by the clusters as
they evolve to using spherical infall models and find that
to of the cluster population lies outside the virial radius
at . For analogous clusters at , we calculate that the ratio
of galaxies that have fallen into the clusters since to those that
were already in the core at that redshift is typically between and
. This wide range of ratios is due to intrinsic scatter and is not a
function of velocity dispersion, so a variety of infall histories is to be
expected for clusters with current velocity dispersions of km s. Within the infall regions of clusters, we find a larger red fraction of galaxies than in the field and
greater clustering among red galaxies than blue. We interpret these findings as
evidence of "preprocessing", where galaxies in denser local environments have
their star formation rates affected prior to their aggregation into massive
clusters, although the possibility of backsplash galaxies complicates the
interpretation.Comment: Accepted for publication in Ap
Halpha-Derived Star-Formation Rates For Three z ~ 0.75 EDisCS Galaxy Clusters
We present Halpha-derived star-formation rates (SFRs) for three z ~ 0.75
galaxy clusters. Our 1 sigma flux limit corresponds to a star-formation rate of
0.10-0.24 solar mass per year, and our minimum reliable Halpha + [N II]
rest-frame equivalent width is 10\AA. We show that Halpha narrowband imaging is
an efficient method for measuring star formation in distant clusters. In two
out of three clusters, we find that the fraction of star-forming galaxies
increases with projected distance from the cluster center. We also find that
the fraction of star-forming galaxies decreases with increasing local galaxy
surface density in the same two clusters. We compare the median rate of star
formation among star-forming cluster galaxies to a small sample of star-forming
field galaxies from the literature and find that the median cluster SFRs are
\~50% less than the median field SFR. We characterize cluster evolution in
terms of the mass-normalized integrated cluster SFR and find that the z ~ 0.75
clusters have more SFR per cluster mass on average than the z <= 0.4 clusters
from the literature. The interpretation of this result is complicated by the
dependence of the mass-normalized SFR on cluster mass and the lack of
sufficient overlap in the mass ranges covered by the low and high redshift
samples. We find that the fraction and luminosities of the brightest starburst
galaxies at z ~ 0.75 are consistent with their being progenitors of the
post-starburst galaxies at z ~ 0.45 if the post-starburst phase lasts several
(~5) times longer than the starburst phase.Comment: Accepted for publication in ApJ, 20 pages, 24 figure
Tissue Classification During Needle Insertion Using Self-Supervised Contrastive Learning and Optical Coherence Tomography
Needle positioning is essential for various medical applications such as
epidural anaesthesia. Physicians rely on their instincts while navigating the
needle in epidural spaces. Thereby, identifying the tissue structures may be
helpful to the physician as they can provide additional feedback in the needle
insertion process. To this end, we propose a deep neural network that
classifies the tissues from the phase and intensity data of complex OCT signals
acquired at the needle tip. We investigate the performance of the deep neural
network in a limited labelled dataset scenario and propose a novel contrastive
pretraining strategy that learns invariant representation for phase and
intensity data. We show that with 10% of the training set, our proposed
pretraining strategy helps the model achieve an F1 score of 0.84 whereas the
model achieves an F1 score of 0.60 without it. Further, we analyse the
importance of phase and intensity individually towards tissue classification
Mass and Redshift Dependence of Star Formation in Relaxed Galaxy Clusters
We investigate the star-formation properties of dynamically relaxed galaxy
clusters as a function of cluster mass for 308 low-redshift clusters drawn from
the Sloan Digital Sky Survey (SDSS) C4 cluster catalog. It is important to
establish if cluster star-formation properties have a mass dependence before
comparing clusters at different epochs, and here we use cluster velocity
dispersion as a measure of cluster mass. We find that the total stellar mass,
the number of star-forming galaxies, and total star-formation rate scale
linearly with the number of member galaxies, with no residual dependence on
cluster velocity dispersion. With the mass-dependence of cluster star-formation
rates established, we compare the SDSS clusters with a sample of z = 0.75
clusters from the literature and find that on average the total H-alpha
luminosity of the high-redshift clusters is 10 times greater than that of the
low-redshift clusters. This can be explained by a decline in the H-alpha
luminosities of individual cluster galaxies by a factor of up to 10 since z =
0.75. The magnitude of this evolution is comparable to that of field galaxies
over a similar redshift interval, and thus the effect of the cluster
environment on the evolution of star-forming galaxies is at most modest. Our
results suggest that the physical mechanism driving the evolution of cluster
star-formation rates is independent of cluster mass, at least for clusters with
velocity dispersion greater than 450 km/s, and operates over a fairly long
timescale such that the star-formation rates of individual galaxies decline by
an order of magnitude over ~7 billion years. (Abridged)Comment: 15 pages; 13 figures; accepted for publication in the Astrophysical
Journa
The Environmental Dependence of the Evolving S0 Fraction
We reinvestigate the dramatic rise in the S0 fraction, f_S0, within clusters
since z ~ 0.5. In particular, we focus on the role of the global galaxy
environment on f_S0 by compiling, either from our own observations or the
literature, robust line-of-sight velocity dispersions, sigma's, for a sample of
galaxy groups and clusters at 0.1 < z < 0.8 that have uniformly determined,
published morphological fractions. We find that the trend of f_S0 with redshift
is twice as strong for sigma < 750 km/s groups/poor clusters than for
higher-sigma, rich clusters. From this result, we infer that over this redshift
range galaxy-galaxy interactions, which are more effective in lower-sigma
environments, are more responsible for transforming spiral galaxies into S0's
than galaxy-environment processes, which are more effective in higher-sigma
environments. The rapid, recent growth of the S0 population in groups and poor
clusters implies that large numbers of progenitors exist in low-sigma systems
at modest redshifts (~ 0.5), where morphologies and internal kinematics are
within the measurement range of current technology.Comment: Accepted for publication in The Astrophysical Journal. 13 pages, 6
figure
Dust-Obscured Star-Formation in Intermediate Redshift Galaxy Clusters
We present Spitzer MIPS 24-micron observations of 16 0.4<z<0.8 galaxy
clusters drawn from the ESO Distant Cluster Survey (EDisCS). This is the first
large 24-micron survey of clusters at intermediate redshift. The depth of our
imaging corresponds to a total IR luminosity of 8x10^10 Lsun, just below the
luminosity of luminous infrared galaxies (LIRGs), and 6^{+1}_{-1}% of M_V < -19
cluster members show 24-micron emission at or above this level. We compare with
a large sample of coeval field galaxies and find that while the fraction of
cluster LIRGs lies significantly below that of the field, the IR luminosities
of the field and cluster galaxies are consistent. However, the stellar masses
of the EDisCS LIRGs are systematically higher than those of the field LIRGs. A
comparison with optical data reveals that ~80% of cluster LIRGs are blue and
the remaining 20% lie on the red sequence. Of LIRGs with optical spectra,
88^{+4}_{-5}% show [O II] emission with EW([O II])>5A, and ~75% exhibit optical
signatures of dusty starbursts. On average, the fraction of cluster LIRGs
increases with projected cluster-centric radius but remains systematically
lower than the field fraction over the area probed (< 1.5xR200). The amount of
obscured star formation declines significantly over the 2.4 Gyr interval
spanned by the EDisCS sample, and the rate of decline is the same for the
cluster and field populations. Our results are consistent with an exponentially
declining LIRG fraction, with the decline in the field delayed by ~1 Gyr
relative to the clusters.Comment: 15 pages, 9 figure
- …