755 research outputs found
Spoken words
Chiefly tablesIncludes bibliographical referencesSupported in part by the National Institute of Education under contract no. US-NIE-C-400-76-011
Learning word meanings from context: How broadly generalizable?
This study investigated incidental learning of word meanings from context during normal reading. A total of 352 students in third, fifth, and seventh grades read either expository or narrative passages selected from grade-level textbooks, and after six days were tested on their knowledge of difficult words from the passages. Small but reliable gains in knowledge of words from the passages read were found at all grade and ability levels. Learning from written context is estimated to account for a third or more of the words acquired annually by school-age children. The results were taken to suggest that getting children to read more should be an effective means for promoting vocabulary growth regardless of grade or ability
Periodic ground state for the charged massive Schwinger model
It is shown that the charged massive Schwinger model supports a periodic
vacuum structure for arbitrary charge density, similar to the common
crystalline layout known in solid state physics. The dynamical origin of the
inhomogeneity is identified in the framework of the bozonized model and in
terms of the original fermionic variables.Comment: 19 pages, 10 figures, revised version, accepted in Phys. Rev.
Design of 280 GHz feedhorn-coupled TES arrays for the balloon-borne polarimeter SPIDER
We describe 280 GHz bolometric detector arrays that instrument the
balloon-borne polarimeter SPIDER. A primary science goal of SPIDER is to
measure the large-scale B-mode polarization of the cosmic microwave background
in search of the cosmic-inflation, gravitational-wave signature. 280 GHz
channels aid this science goal by constraining the level of B-mode
contamination from galactic dust emission. We present the focal plane unit
design, which consists of a 1616 array of conical, corrugated feedhorns
coupled to a monolithic detector array fabricated on a 150 mm diameter silicon
wafer. Detector arrays are capable of polarimetric sensing via waveguide
probe-coupling to a multiplexed array of transition-edge-sensor (TES)
bolometers. The SPIDER receiver has three focal plane units at 280 GHz, which
in total contains 765 spatial pixels and 1,530 polarization sensitive
bolometers. By fabrication and measurement of single feedhorns, we demonstrate
14.7 FHWM Gaussian-shaped beams with 1% ellipticity in a 30%
fractional bandwidth centered at 280 GHz. We present electromagnetic
simulations of the detection circuit, which show 94% band-averaged,
single-polarization coupling efficiency, 3% reflection and 3% radiative loss.
Lastly, we demonstrate a low thermal conductance bolometer, which is
well-described by a simple TES model and exhibits an electrical noise
equivalent power (NEP) = 2.6 10 W/,
consistent with the phonon noise prediction.Comment: Proceedings of SPIE Astronomical Telescopes + Instrumentation 201
The Thermal Design, Characterization, and Performance of the SPIDER Long-Duration Balloon Cryostat
We describe the SPIDER flight cryostat, which is designed to cool six
millimeter-wavelength telescopes during an Antarctic long-duration balloon
flight. The cryostat, one of the largest to have flown on a stratospheric
payload, uses liquid helium-4 to deliver cooling power to stages at 4.2 and 1.6
K. Stainless steel capillaries facilitate a high flow impedance connection
between the main liquid helium tank and a smaller superfluid tank, allowing the
latter to operate at 1.6 K as long as there is liquid in the 4.2 K main tank.
Each telescope houses a closed cycle helium-3 adsorption refrigerator that
further cools the focal planes down to 300 mK. Liquid helium vapor from the
main tank is routed through heat exchangers that cool radiation shields,
providing negative thermal feedback. The system performed successfully during a
17 day flight in the 2014-2015 Antarctic summer. The cryostat had a total hold
time of 16.8 days, with 15.9 days occurring during flight.Comment: 15 pgs, 17 fig
Pointing control for the SPIDER balloon-borne telescope
We present the technology and control methods developed for the pointing
system of the SPIDER experiment. SPIDER is a balloon-borne polarimeter designed
to detect the imprint of primordial gravitational waves in the polarization of
the Cosmic Microwave Background radiation. We describe the two main components
of the telescope's azimuth drive: the reaction wheel and the motorized pivot. A
13 kHz PI control loop runs on a digital signal processor, with feedback from
fibre optic rate gyroscopes. This system can control azimuthal speed with <
0.02 deg/s RMS error. To control elevation, SPIDER uses stepper-motor-driven
linear actuators to rotate the cryostat, which houses the optical instruments,
relative to the outer frame. With the velocity in each axis controlled in this
way, higher-level control loops on the onboard flight computers can implement
the pointing and scanning observation modes required for the experiment. We
have accomplished the non-trivial task of scanning a 5000 lb payload
sinusoidally in azimuth at a peak acceleration of 0.8 deg/s, and a peak
speed of 6 deg/s. We can do so while reliably achieving sub-arcminute pointing
control accuracy.Comment: 20 pages, 12 figures, Presented at SPIE Ground-based and Airborne
Telescopes V, June 23, 2014. To be published in Proceedings of SPIE Volume
914
Efficient Generation of Germ Line Transmitting Chimeras from C57BL/6N ES Cells by Aggregation with Outbred Host Embryos
Genetically modified mouse strains derived from embryonic stem (ES) cells have become essential tools for functional genomics and biomedical research. Large scale mutagenesis projects are producing libraries of mutant C57BL/6 (B6) ES cells to enable the functional annotation of every gene of the mouse genome. To realize the utility of these resources, efficient and accessible methods of generating mutant mice from these ES cells are necessary. Here, we describe a combination of ICR morula aggregation and a chemically-defined culture medium with widely available and accessible components for the high efficiency generation of germline transmitting chimeras from C57BL/6N ES cells. Together these methods will ease the access of the broader biomedical research community to the publicly available B6 ES cell resources
Harnessing the NEON data revolution to advance open environmental science with a diverse and data-capable community
It is a critical time to reflect on the National Ecological Observatory Network (NEON) science to date as well as envision what research can be done right now with NEON (and other) data and what training is needed to enable a diverse user community. NEON became fully operational in May 2019 and has pivoted from planning and construction to operation and maintenance. In this overview, the history of and foundational thinking around NEON are discussed. A framework of open science is described with a discussion of how NEON can be situated as part of a larger data constellation—across existing networks and different suites of ecological measurements and sensors. Next, a synthesis of early NEON science, based on \u3e100 existing publications, funded proposal efforts, and emergent science at the very first NEON Science Summit (hosted by Earth Lab at the University of Colorado Boulder in October 2019) is provided. Key questions that the ecology community will address with NEON data in the next 10 yr are outlined, from understanding drivers of biodiversity across spatial and temporal scales to defining complex feedback mechanisms in human–environmental systems. Last, the essential elements needed to engage and support a diverse and inclusive NEON user community are highlighted: training resources and tools that are openly available, funding for broad community engagement initiatives, and a mechanism to share and advertise those opportunities. NEON users require both the skills to work with NEON data and the ecological or environmental science domain knowledge to understand and interpret them. This paper synthesizes early directions in the community’s use of NEON data, and opportunities for the next 10 yr of NEON operations in emergent science themes, open science best practices, education and training, and community building
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