11,353 research outputs found
Electrophysiological analysis of transcranial direct current stimulation and its effect on cortical spreading depression
Transcranial direct current stimulation (TDCS) allows for the noninvasive modulation of cortical activity. In this study, the effects of cathodal and anodal TDCS treatment on baseline activity in the motor cortex of rats were investigated via translaminar electroencephalogram (EEG) recording and power spectral density analysis. Treatment with low intensity anodal TDCS for five minutes was found to increase delta and theta frequency cortical activity during and for up to five minutes following treatment.
This study also assessed the interaction of TDCS with the phenomenon of cortical spreading depression (CoSD), which has been implicated in numerous disease states, including migraine and stroke. TDCS treatment was given concurrently with induction of CoSD via administration of potassium chloride to the surface of the dura. The presence of the spreading depression event, a characteristic low frequency wave observed to travel outwards from the point of CoSD induction and downwards through the cortex, was used as a proxy measure for the occurrence of CoSD. It was observed that animals treated with cathodal TDCS exhibited fewer spreading depression events relative to those treated with anodal TDCS or those receiving sham treatment.
In this study, animals were segregated into groups that exhibited stimulus artifact during TDCS treatment and those that did not. Stimulus artifact was defined as a characteristic alpha and/or beta frequency activity spike lasting throughout and not longer than the period of stimulation. Those animals receiving TDCS without exhibiting stimulus artifact were considered for the purposes of this study to not have received proper TDCS treatment, and acted as a sham treatment group. Because salient differences emerged between the stimulus artifact positive and stimulus artifact negative groups, this study suggests that the presence of stimulus artifact could be used as a proxy measure for successful TDCS dosage
Distributional Inclusion Vector Embedding for Unsupervised Hypernymy Detection
Modeling hypernymy, such as poodle is-a dog, is an important generalization
aid to many NLP tasks, such as entailment, coreference, relation extraction,
and question answering. Supervised learning from labeled hypernym sources, such
as WordNet, limits the coverage of these models, which can be addressed by
learning hypernyms from unlabeled text. Existing unsupervised methods either do
not scale to large vocabularies or yield unacceptably poor accuracy. This paper
introduces distributional inclusion vector embedding (DIVE), a
simple-to-implement unsupervised method of hypernym discovery via per-word
non-negative vector embeddings which preserve the inclusion property of word
contexts in a low-dimensional and interpretable space. In experimental
evaluations more comprehensive than any previous literature of which we are
aware-evaluating on 11 datasets using multiple existing as well as newly
proposed scoring functions-we find that our method provides up to double the
precision of previous unsupervised embeddings, and the highest average
performance, using a much more compact word representation, and yielding many
new state-of-the-art results.Comment: NAACL 201
Monte Carlo modeling of low-energy electron-induced secondary electron emission yields in micro-architected boron nitride surfaces
Surface erosion and secondary electron emission (SEE) have been identified as
the most critical life-limiting factors in channel walls of Hall-effect
thrusters for space propulsion. Recent wall concepts based on micro-architected
surfaces have been proposed to mitigate surface erosion and SEE. The idea
behind these designs is to take advantage of very-high surface-to-volume ratios
to reduce SEE and ion erosion by internal trapping and redeposition. This has
resulted in renewed interest to study electron-electron processes in relevant
thruster wall materials. In this work, we present calculations of SEE yields in
micro-porous hexagonal BN surfaces using stochastic simulations of
electron-material interactions in discretized surface geometries. Our model
consists of two complementary parts. First we study SEE as a function of
primary electron energy and incidence angle in flat surfaces using Monte Carlo
simulations of electron multi-scattering processes. The results are then used
to represent the response function of discrete surface elements to individual
electron rays generated using a ray-tracing Monte Carlo model. We find that
micro-porous surfaces result in SEE yield reductions of over 50% in the energy
range experienced in Hall thrusters. This points to the suitability of these
micro-architected surface concepts to mitigate SEE-related issues in compact
electric propulsion devices
Creating a Model Medical Student-Run “Free” Clinic: La Casita de la Salud-The New York Medical College Student-Run Clinic
La Casita de la Salud, The New York Medical College Student-Run Clinic, opened its doors in 2005, to service the medically underserved population of East Harlem, New York City. This article discusses how the organization came to be, and the reasoning behind its multi-faceted implemented interventions to decrease health disparities through cultural competency, patient education, community integration, and preventative medicine. For more information on La Casita de la Salud, please see http://nymclacasita.org
Daily Timed Sexual Interaction Induces Moderate Anticipatory Activity in Mice
Anticipation of resource availability is a vital skill yet it is poorly understood in terms of neuronal circuitry. Rodents display robust anticipatory activity in the several hours preceding timed daily access to food when access is limited to a short temporal duration. We tested whether this anticipatory behavior could be generalized to timed daily social interaction by examining if singly housed male mice could anticipate either a daily novel female or a familiar female. We observed that anticipatory activity was moderate under both conditions, although both a novel female partner and sexual experience are moderate contributing factors to increasing anticipatory activity. In contrast, restricted access to running wheels did not produce any anticipatory activity, suggesting that an increase in activity during the scheduled access time was not sufficient to induce anticipation. To tease apart social versus sexual interaction, we tested the effect of exposing singly housed female mice to a familiar companion female mouse daily. The female mice did not show anticipatory activity for restricted female access, despite a large amount of social interaction, suggesting that daily timed social interaction between mice of the same gender is insufficient to induce anticipatory activity. Our study demonstrates that male mice will show anticipatory activity, albeit inconsistently, for a daily timed sexual encounter
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