8,585 research outputs found
Effects of carbon fibers on consumer products
The potential effects of carbon fibers on consumer products such as dishwashers, microwave ovens, and smoke detectors were investigated. The investigation was divided into two categories to determine the potential faults and hazards that could occur if fibers should enter the electrical circuits of the selected appliances. The categories were a fault analysis and a hazard analysis. Hazards considered were fire, flood, physical harm, explosion, and electrical shock. Electrical shock was found to be a possible occurrence related to carbon fibers. Faults were considered to be any effect on the performance of an appliance which would result in complaint or require service action
A New Pathway for the Preparation of Highly Qualified Teachers: The Master of Arts in Teaching (MAT)
This article reports on the development and initial implementation of a Master of Arts in Teaching (MAT) degree, an accelerated graduate program that encourages and scaffolds individuals with existing disciplinary expertise in entering the teaching profession. First, the context for developing the program is outlined. Next, the unique structure of the 15-month program, which consists of three blocks, is described. Expectations about students are then shared, quality control features of the program are highlighted, and the lessons we learned about program development and implementation are detailed. Finally, thoughts about the future of this program and others of its type are shared based upon our experience
Space suit
A pressure suit for high altitude flights, particularly space missions is reported. The suit is designed for astronauts in the Apollo space program and may be worn both inside and outside a space vehicle, as well as on the lunar surface. It comprises an integrated assembly of inner comfort liner, intermediate pressure garment, and outer thermal protective garment with removable helmet, and gloves. The pressure garment comprises an inner convoluted sealing bladder and outer fabric restraint to which are attached a plurality of cable restraint assemblies. It provides versitility in combination with improved sealing and increased mobility for internal pressures suitable for life support in the near vacuum of outer space
The Breakfast Food Challenge: Helping to Meet Personal Needs in the Science Classroom
One of the four Project Synthesis goal clusters for science education focuses on meeting the personal needs of students who are maturing in a scientific/technological society. Many existing science programs fall short in this regard, particularly if teachers are seriously interested in changing learner behavior for the better. One component of learner behavior that is highly consistent with the personal needs goal cluster of Project Synthesis is helping students become more intelligent consumers in a scientific society
Fully-Coupled Simulation of Cosmic Reionization. I: Numerical Methods and Tests
We describe an extension of the Enzo code to enable fully-coupled radiation
hydrodynamical simulation of inhomogeneous reionization in large cosmological volumes with thousands to millions of point sources. We
solve all dynamical, radiative transfer, thermal, and ionization processes
self-consistently on the same mesh, as opposed to a postprocessing approach
which coarse-grains the radiative transfer. We do, however, employ a simple
subgrid model for star formation which we calibrate to observations. Radiation
transport is done in the grey flux-limited diffusion (FLD) approximation, which
is solved by implicit time integration split off from the gas energy and
ionization equations, which are solved separately. This results in a faster and
more robust scheme for cosmological applications compared to the earlier
method. The FLD equation is solved using the hypre optimally scalable geometric
multigrid solver from LLNL. By treating the ionizing radiation as a grid field
as opposed to rays, our method is scalable with respect to the number of
ionizing sources, limited only by the parallel scaling properties of the
radiation solver. We test the speed and accuracy of our approach on a number of
standard verification and validation tests. We show by direct comparison with
Enzo's adaptive ray tracing method Moray that the well-known inability of FLD
to cast a shadow behind opaque clouds has a minor effect on the evolution of
ionized volume and mass fractions in a reionization simulation validation test.
We illustrate an application of our method to the problem of inhomogeneous
reionization in a 80 Mpc comoving box resolved with Eulerian grid
cells and dark matter particles.Comment: 32 pages, 23 figures. ApJ Supp accepted. New title and substantial
revisions re. v
X-ray Supercavities in the Hydra A Cluster and the Outburst History of the Central Galaxy's Active Nucleus
A 227 ksec Chandra Observatory X-ray image of the hot plasma in the Hydra A
cluster has revealed an extensive cavity system. The system was created by a
continuous outflow or a series of bursts from the nucleus of the central galaxy
over the past 200-500 Myr. The cavities have displaced 10% of the plasma within
a 300 kpc radius of the central galaxy, creating a swiss-cheese-like topology
in the hot gas. The surface brightness decrements are consistent with empty
cavities oriented within 40 degrees of the plane of the sky. The outflow has
deposited upward of 10^61 erg into the cluster gas, most of which was propelled
beyond the inner ~100 kpc cooling region. The supermassive black hole has
accreted at a rate of approximately 0.1-0.25 solar masses per year over this
time frame, which is a small fraction of the Eddington rate of a ~10^9 solar
mass black hole, but is dramatically larger than the Bondi rate. Given the
previous evidence for a circumnuclear disk of cold gas in Hydra A, these
results are consistent with the AGN being powered primarily by infalling cold
gas. The cavity system is shadowed perfectly by 330 MHz radio emission. Such
low frequency synchrotron emission may be an excellent proxy for X-ray cavities
and thus the total energy liberated by the supermassive black hole.Comment: 8 pages, 3 figures; Submitted to ApJ, revised per referee's
suggestion
An Energetic AGN Outburst Powered by a Rapidly Spinning Supermassive Black Hole or an Accreting Ultramassive Black Hole
Powering the 10^62 erg nuclear outburst in the MS0735.6+7421 cluster central
galaxy by accretion implies that its supermassive black hole (SMBH) grew by
~6x10^8 solar masses over the past 100 Myr. We place upper limits on the amount
of cold gas and star formation near the nucleus of <10^9 solar masses and <2
solar masses per year, respectively. These limits imply that an implausibly
large fraction of the preexisting cold gas in the bulge must have been consumed
by its SMBH at the rate of ~3-5 solar masses per year while leaving no trace of
star formation. Such a high accretion rate would be difficult to maintain by
stellar accretion or the Bondi mechanism, unless the black hole mass approaches
10^11 solar masses. Its feeble nuclear luminosities in the UV, I, and X-ray
bands compared to its enormous mechanical power are inconsistent with rapid
accretion onto a ~5x10^9 solar mass black hole. We suggest instead that the AGN
outburst is powered by a rapidly-spinning black hole. A maximally-spinning,
10^9 solar mass black hole contains enough rotational energy, ~10^62 erg, to
quench a cooling flow over its lifetime and to contribute significantly to the
excess entropy found in the hot atmospheres of groups and clusters. Two modes
of AGN feedback may be quenching star formation in elliptical galaxies centered
in cooling halos at late times. An accretion mode that operates in gas-rich
systems, and a spin mode operating at modest accretion rates. The spin
conjecture may be avoided in MS0735 by appealing to Bondi accretion onto a
central black hole whose mass greatly exceeds 10^10 solar mass. The host
galaxy's unusually large, 3.8 kpc stellar core radius (light deficit) may
witness the presence of an ultramassive black hole.Comment: Accepted for publication in ApJ. Modifications: adopted slightly
higher black hole mass using Lauer's M_SMBH vs L_bulge relation and adjusted
related quantities; considered more seriously the consequences of a
ultramassive black hole, motivated by new Kormendy & Bender paper published
after our submission; other modifications per referee comments by Ruszkowsk
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