955 research outputs found
CLAS+FROST: new generation of photoproduction experiments at Jefferson Lab
A large part of the experimental program in Hall B of the Jefferson Lab is
dedicated to baryon spectroscopy. Photoproduction experiments are essential
part of this program. CEBAF Large Acceptance Spectrometer (CLAS) and
availability of circularly and linearly polarized tagged photon beams provide
unique conditions for this type of experiments. Recent addition of the Frozen
Spin Target (FROST) gives a remarkable opportunity to measure double and triple
polarization observables for different pseudo-scalar meson photoproduction
processes. For the first time, a complete or nearly complete experiment becomes
possible and will allow model independent extraction of the reaction amplitude.
An overview of the experiment and its current status is presented.Comment: 6 pages, 7 figures. Invited paper NSTAR 2009 conferenc
Audio tapes vs. interactive computer software for studying bird songs: The value of active learning
We tested the use of audio tapes versus interactive computer software for learning of bird songs by undergraduate students at the University of Missouri. Overall final grades did not differ between semesters when audio tapes or computer software were used to study bird songs. Mean song quiz scores were higher (21.63 vs 19.48; 25 maximum, P=0.04) and mean quiz score variances lower (0.49 vs. 0.75, P=0.007) when students had access to interactive computer software than when they used audio tapes to study bird songs. Key factors affecting improved student performance seemed to be higher student interactions and peer teaching activity, self-testing options, and ease of access to specific quiz material provided by interactive computer software
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Validation of machine learning models to detect amyloid pathologies across institutions.
Semi-quantitative scoring schemes like the Consortium to Establish a Registry for Alzheimer's Disease (CERAD) are the most commonly used method in Alzheimer's disease (AD) neuropathology practice. Computational approaches based on machine learning have recently generated quantitative scores for whole slide images (WSIs) that are highly correlated with human derived semi-quantitative scores, such as those of CERAD, for Alzheimer's disease pathology. However, the robustness of such models have yet to be tested in different cohorts. To validate previously published machine learning algorithms using convolutional neural networks (CNNs) and determine if pathological heterogeneity may alter algorithm derived measures, 40 cases from the Goizueta Emory Alzheimer's Disease Center brain bank displaying an array of pathological diagnoses (including AD with and without Lewy body disease (LBD), and / or TDP-43-positive inclusions) and levels of Aβ pathologies were evaluated. Furthermore, to provide deeper phenotyping, amyloid burden in gray matter vs whole tissue were compared, and quantitative CNN scores for both correlated significantly to CERAD-like scores. Quantitative scores also show clear stratification based on AD pathologies with or without additional diagnoses (including LBD and TDP-43 inclusions) vs cases with no significant neurodegeneration (control cases) as well as NIA Reagan scoring criteria. Specifically, the concomitant diagnosis group of AD + TDP-43 showed significantly greater CNN-score for cored plaques than the AD group. Finally, we report that whole tissue computational scores correlate better with CERAD-like categories than focusing on computational scores from a field of view with densest pathology, which is the standard of practice in neuropathological assessment per CERAD guidelines. Together these findings validate and expand CNN models to be robust to cohort variations and provide additional proof-of-concept for future studies to incorporate machine learning algorithms into neuropathological practice
Development of silicon nitride and cermet resistors for use in a binary counter, metal insulator field effect transistor circuit Final report, 1 Dec. 1966 - 31 Mar. 1968
Silicon nitride and cermet resistors for binary counter metal insulator field effect transistor circui
The homotopy theory of dg-categories and derived Morita theory
The main purpose of this work is the study of the homotopy theory of
dg-categories up to quasi-equivalences. Our main result provides a natural
description of the mapping spaces between two dg-categories and in
terms of the nerve of a certain category of -bimodules. We also prove
that the homotopy category is cartesian closed (i.e. possesses
internal Hom's relative to the tensor product). We use these two results in
order to prove a derived version of Morita theory, describing the morphisms
between dg-categories of modules over two dg-categories and as the
dg-category of -bi-modules. Finally, we give three applications of our
results. The first one expresses Hochschild cohomology as endomorphisms of the
identity functor, as well as higher homotopy groups of the \emph{classifying
space of dg-categories} (i.e. the nerve of the category of dg-categories and
quasi-equivalences between them). The second application is the existence of a
good theory of localization for dg-categories, defined in terms of a natural
universal property. Our last application states that the dg-category of
(continuous) morphisms between the dg-categories of quasi-coherent (resp.
perfect) complexes on two schemes (resp. smooth and proper schemes) is
quasi-equivalent to the dg-category of quasi-coherent complexes (resp. perfect)
on their product.Comment: 50 pages. Few mistakes corrected, and some references added. Thm.
8.15 is new. Minor corrections. Final version, to appear in Inventione
Towers and fibered products of model categories
Given a left Quillen presheaf of localized model structures, we study the homotopy limit model structure on the associated category of sections. We focus specifically on towers and fibered products of model categories. As applications we consider Postnikov towers of model categories, chromatic towers of spectra and Bousfield arithmetic squares of spectra. For spectral model categories, we show that the homotopy fiber of a stable left Bousfield localization is a stable right Bousfield localization
Homological Localisation of Model Categories
One of the most useful methods for studying the stable homotopy category is localising at some spectrum E. For an arbitrary stable model category we introduce a candidate
for the E–localisation of this model category. We study the properties of this new construction and relate it to some well–known categories
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