503 research outputs found
Comparison of Blood and Brain Mercury Levels in Infant Monkeys Exposed to Methylmercury or Vaccines Containing Thimerosal
Thimerosal is a preservative that has been used in manufacturing vaccines since the 1930s. Reports have indicated that infants can receive ethylmercury (in the form of thimerosal) at or above the U.S. Environmental Protection Agency guidelines for methylmercury exposure, depending on the exact vaccinations, schedule, and size of the infant. In this study we compared the systemic disposition and brain distribution of total and inorganic mercury in infant monkeys after thimerosal exposure with those exposed to MeHg. Monkeys were exposed to MeHg (via oral gavage) or vaccines containing thimerosal (via intramuscular injection) at birth and 1, 2, and 3 weeks of age. Total blood Hg levels were determined 2, 4, and 7 days after each exposure. Total and inorganic brain Hg levels were assessed 2, 4, 7, or 28 days after the last exposure. The initial and terminal half-life of Hg in blood after thimerosal exposure was 2.1 and 8.6 days, respectively, which are significantly shorter than the elimination half-life of Hg after MeHg exposure at 21.5 days. Brain concentrations of total Hg were significantly lower by approximately 3-fold for the thimerosal-exposed monkeys when compared with the MeHg infants, whereas the average brain-to-blood concentration ratio was slightly higher for the thimerosal-exposed monkeys (3.5 ± 0.5 vs. 2.5 ± 0.3). A higher percentage of the total Hg in the brain was in the form of inorganic Hg for the thimerosal-exposed monkeys (34% vs. 7%). The results indicate that MeHg is not a suitable reference for risk assessment from exposure to thimerosal-derived Hg. Knowledge of the toxicokinetics and developmental toxicity of thimerosal is needed to afford a meaningful assessment of the developmental effects of thimerosal-containing vaccines
âCourseâ Work: Pinar's Currere as an Initiation into Curriculum Studies
In this article, four new doctoral students reflect on Pinarâs currere process as an initiation into the discipline of curriculum studies. Currere involves examining oneâs experiences as curricula that shape understandings: each of us undertook the steps of currere individually and then shared our reflections through collaborative autobiography. This collaboration expanded our self-reflexivity in relation to curriculum and to discursive contexts and, unexpectedly, created an authentic learning community. The currere process has not only written us into curriculum studies, but also compelled us to âparticipate in the constitution and transformation of ourselvesâ (Pinar, 1994, p. 74) that is so vital to our work in education. The following articleâwhich consists of collaborative and personal writingâdescribes a valuable practice for bringing graduate students into curriculum studies. It also considers whether the self-reflexivity encouraged by currere might still be relevant for contemporary scholars and educators almost four decades after its inception
Trauma in Veterans with Substance Use Disorder: Similar Treatment Need among Urban and Rural Residents
Purpose: The objective of this study is to determine whether rural residence is associated with trauma exposure or posttraumatic stress disorder symptoms among military veterans seeking treatment for substance use disorder (SUD) through the Department of Veterans Affairs (VA). Delivering mental health services to veterans in rural areas is a challenge, so identifying differences in the causes and outcomes of trauma exposure would assist in effectively targeting service delivery.
Methods: Veterans (N = 196) entering SUD treatment at 3 Midwestern VA treatment centers were designated as either urban or rural, based on rural-urban commuting area (RUCA) codes. The veterans completed the Life Events Checklist, the Posttraumatic Stress Disorder Checklist, and the Addiction Severity Indexâs psychiatric status subscale. Hypothesized relationships between rural-urban residence and both trauma exposure and symptomology were tested using independent samples t tests, chi-square tests, and ordinary least squares regression.
Findings: The range of traumatic experiences was similar between rural and urban veterans, and rural-urban residence was not significantly associated with the overall array of traumas experienced or the symptom measuresâ overall scores or subscores. Of 17 possible traumatic lifetime experiences, rural veterans differed from urban veterans on only 2, reporting significantly lower rates of transportation accidents and unwanted sexual experiences.
Conclusions: In both the causes of trauma and the need for treatment, veterans residing in rural areas differ little from their urban counterparts
Surviving drought: a framework for understanding animal responses to small rain events in the arid zone
Large rain events drive dramatic resource pulses and the complex pulseâreserve dynamics of arid ecosystems change between highârain years and drought. However, aridâzone animal responses to shortâterm changes in climate are unknown, particularly smaller rain events that briefly interrupt longerâterm drought. Using arthropods as model animals, we determined the effects of a small rain event on arthropod abundance in western New South Wales, Australia during a longerâterm shift toward drought. Arthropod abundance decreased over 2 yr, but captures of 10 out of 15 ordinal taxa increased dramatically after the small rain event (\u3c40 \u3emm). The magnitude of increases ranged from 10.4 million% (collembolans) to 81% (spiders). After 3 months, most taxa returned to prerain abundance. However, small soilâdwelling beetles, mites, spiders, and collembolans retained high abundances despite the onset of winter temperatures and lack of subsequent rain. As predicted by pulseâreserve models, most aridâzone arthropod populations declined during drought. However, small rain events may play a role in buffering some taxa from declines during longerâterm drought or other xenobiotic influences. We outline the framework for a new model of animal responses to environmental conditions in the arid zone, as some species clearly benefit from rain inputs that do not dramatically influence primary productivity
Benchmarking Representation Learning for Natural World Image Collections
Recent progress in self-supervised learning has resulted in models that are
capable of extracting rich representations from image collections without
requiring any explicit label supervision. However, to date the vast majority of
these approaches have restricted themselves to training on standard benchmark
datasets such as ImageNet. We argue that fine-grained visual categorization
problems, such as plant and animal species classification, provide an
informative testbed for self-supervised learning. In order to facilitate
progress in this area we present two new natural world visual classification
datasets, iNat2021 and NeWT. The former consists of 2.7M images from 10k
different species uploaded by users of the citizen science application
iNaturalist. We designed the latter, NeWT, in collaboration with domain experts
with the aim of benchmarking the performance of representation learning
algorithms on a suite of challenging natural world binary classification tasks
that go beyond standard species classification. These two new datasets allow us
to explore questions related to large-scale representation and transfer
learning in the context of fine-grained categories. We provide a comprehensive
analysis of feature extractors trained with and without supervision on ImageNet
and iNat2021, shedding light on the strengths and weaknesses of different
learned features across a diverse set of tasks. We find that features produced
by standard supervised methods still outperform those produced by
self-supervised approaches such as SimCLR. However, improved self-supervised
learning methods are constantly being released and the iNat2021 and NeWT
datasets are a valuable resource for tracking their progress.Comment: CVPR 202
Submm/mm Galaxy Counterpart Identification Using a Characteristic Density Distribution
We present a new submm/mm galaxy counterpart identification technique which
builds on the use of Spitzer IRAC colors as discriminators between likely
counterparts and the general IRAC galaxy population. Using 102 radio- and
SMA-confirmed counterparts to AzTEC sources across three fields (GOODS-N,
GOODS-S, and COSMOS), we develop a non-parametric IRAC color-color
characteristic density distribution (CDD), which, when combined with positional
uncertainty information via likelihood ratios, allows us to rank all potential
IRAC counterparts around SMGs and calculate the significance of each ranking
via the reliability factor. We report all robust and tentative radio
counterparts to SMGs, the first such list available for AzTEC/COSMOS, as well
as the highest ranked IRAC counterparts for all AzTEC SMGs in these fields as
determined by our technique. We demonstrate that the technique is free of radio
bias and thus applicable regardless of radio detections. For observations made
with a moderate beamsize (~18"), this technique identifies ~85 per cent of SMG
counterparts. For much larger beamsizes (>30"), we report identification rates
of 33-49 per cent. Using simulations, we demonstrate that this technique is an
improvement over using positional information alone for observations with
facilities such as AzTEC on the LMT and SCUBA-2 on JCMT.Comment: 30 pages, 9 figures, 5 tables. Accepted for publication in MNRA
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