306 research outputs found
A method for reducing animal use whilst maintaining statistical power in electrophysiological recordings from rodent nerves
The stimulus evoked compound action potential, recorded from ex vivo nerve trunks such as the rodent optic and sciatic nerve, is a popular model system used to study aspects of nervous system metabolism. This includes (1) the role of glycogen in supporting axon conduction, (2) the injury mechanisms resulting from metabolic insults, and (3) to test putative benefits of clinically relevant neuroprotective strategies. We demonstrate the benefit of simultaneously recording from pairs of nerves in the same superfusion chamber compared with conventional recordings from single nerves. Experiments carried out on mouse optic and sciatic nerves demonstrate that our new recording configuration decreased the relative standard deviation from samples when compared with recordings from an equivalent number of individually recorded nerves. The new method reduces the number of animals required to produce equivalent Power compared with the existing method, where single nerves are used. Adopting this method leads to increased experimental efficiency and productivity. We demonstrate that reduced animal use and increased Power can be achieved by recording from pairs of rodent nerve trunks simultaneously
An evaluation of a service program in reading in grades one through six,
Includes tests in separate folders in back of dissertation.
Thesis (M.A.)--Boston Universit
ROSAT X-ray Spectral Properties of Nearby Young Associations: TW Hydrae, Tucana-Horologium, and the beta Pic Moving Group
We present archival ROSAT data for three recently identified, nearby (D<70
pc), young (~10-40 Myr) stellar associations: the TW Hydrae Association, the
Tucana-Horologium Association, and the beta Pic Moving Group. The distributions
of ROSAT X-ray hardness ratios (HR1, HR2) for these three groups, whose
membership is dominated by low-mass, weak-lined T Tauri stars, are tightly
clustered and very similar to one another. The value of HR1 for TW Hya itself
-- the only bona fide classical T Tauri star in any of the nearby groups -- is
clearly anomalous among these nearby young stars. We compare the hardness ratio
distributions of stars in the three nearby groups with those of T Tauri stars,
the Hyades, and main sequence dwarfs in the field. This comparison demonstrates
that the X-ray spectra of F through M stars soften with age, and that F and G
stars evolve more rapidly in X-ray spectral hardness than do K and M stars. It
is as yet unclear whether this trend can be attributed to age-dependent changes
in the intrinsic X-ray spectra of stars of type F and later, to a decrease in
the column density of circumstellar gas (e.g., in residual protoplanetary
disks), or to the diminishing contributions of star-disk interactions to X-ray
emission. Regardless, these results demonstrate that analysis of archival ROSAT
X-ray spectral data can help both to identify nearby, young associations and to
ascertain the X-ray emission properties of members of known associations.Comment: 17 pages, 4 figures; accepted by the Astrophysical Journa
Mid-latitude continental temperatures through the early Eocene in western Europe
Branched glycerol dialkyl glycerol tetraethers (brGDGTs) are increasingly used to reconstruct mean annual air temperature (MAAT) during the early Paleogene. However, the application of this proxy in coal deposits is limited and brGDGTs have only been detected in immature coals (i.e. lignites). Using samples recovered from Schöningen, Germany (âŒ48°N palaeolatitude), we provide the first detailed study into the occurrence and distribution of brGDGTs through a sequence of early Eocene lignites and associated interbeds. BrGDGTs are abundant and present in every sample. In comparison to modern studies, changes in vegetation type do not appear to significantly impact brGDGT distributions; however, there are subtle differences between lignites â representing peat-forming environments â and siliciclastic nearshore marine interbed depositional environments. Using the most recent brGDGT temperature calibration (MATmr) developed for soils, we generate the first continental temperature record from central-western continental Europe through the early Eocene. Lignite-derived MAAT estimates range from 23 to 26â°C while those derived from the nearshore marine interbeds exceed 20â°C. These estimates are consistent with other mid-latitude environments and model simulations, indicating enhanced mid-latitude, early Eocene warmth. In the basal part of the section studied, warming is recorded in both the lignites (âŒ2â°C) and nearshore marine interbeds (âŒ2â3â°C). This culminates in a long-term temperature maximum, likely including the Early Eocene Climatic Optimum (EECO). Although this long-term warming trend is relatively well established in the marine realm, it has rarely been shown in terrestrial settings. Using a suite of model simulations we show that the magnitude of warming at Schöningen is broadly consistent with a doubling of CO2, in agreement with late Paleocene and early Eocene pCO2 estimates
Towards Fairer Datasets: Filtering and Balancing the Distribution of the People Subtree in the ImageNet Hierarchy
Computer vision technology is being used by many but remains representative
of only a few. People have reported misbehavior of computer vision models,
including offensive prediction results and lower performance for
underrepresented groups. Current computer vision models are typically developed
using datasets consisting of manually annotated images or videos; the data and
label distributions in these datasets are critical to the models' behavior. In
this paper, we examine ImageNet, a large-scale ontology of images that has
spurred the development of many modern computer vision methods. We consider
three key factors within the "person" subtree of ImageNet that may lead to
problematic behavior in downstream computer vision technology: (1) the stagnant
concept vocabulary of WordNet, (2) the attempt at exhaustive illustration of
all categories with images, and (3) the inequality of representation in the
images within concepts. We seek to illuminate the root causes of these concerns
and take the first steps to mitigate them constructively.Comment: Accepted to FAT* 202
Banks' risk assessment of Swedish SMEs
Building on the literatures on asymmetric information and risk taking, this paper applies conjoint experiments to investigate lending officers' probabilities of supporting credit to established or existing SMEs. Using a sample of 114 Swedish lending officers, we test hypotheses concerning how information on the borrower's ability to repay the loan; alignment of risk preferences; and risk sharing affect their willingness to grant credit. Results suggest that features that reduce the risk to the bank and shift the risk to the borrower have the largest impact. The paper highlights the interaction between factors that influence the credit decision. Implications for SMEs, banks and research are discussed
High School Quality is Associated with Cognition 58 Years Later
We leveraged a unique school-based longitudinal cohortâthe Project Talent Aging Studyâto examine whether attending higher quality schools is associated with cognitive performance among older adults in the United States (mean age = 74.8). Participants (n = 2,289) completed telephone neurocognitive testing. Six indicators of high school quality, reported by principals at the time of schooling, were predictors of respondentsâ cognitive function 58 years later. To account for school-clustering, multilevel linear and logistic models were applied. We found that attending schools with a higher number of teachers with graduate training was the clearest predictor of later-life cognition, and school quality mattered especially for language abilities. Importantly, Black respondents (n = 239; 10.5 percentage) were disproportionately exposed to low quality high schools. Therefore, increased investment in schools, especially those that serve Black children, could be a powerful strategy to improve later life cognitive health among older adults in the United States
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