33,496 research outputs found
Innovative Opportunities for Elementary and Middle School Teachers to Maintain Currency in Mathematics and Science: A Community College-School System Partnership
Since 1992 the Manassas Campus of Northern Virginia Community College – in response to requests from local school systems – has developed four innovative methods of assisting elementary, secondary and middle school teachers to enhance their content knowledge in science and mathematics, as well as integrate curriculum units for classroom presentation. These methods are based on the assumptions that: - While teachers at this level have fundamental understanding of math and science, if they wish to incorporate new concepts or technologies from these fields, graduate level content courses are generally beyond their background level. - Community College faculty can often provide a bridge that connects advanced content in science and mathematics with the applications that can be adapted to elementary/middle school curriculum. - Presenting content to a mixed audience of teachers from K-8 allows teachers to see how content can be adapted to grade levels above and below. - Content delivery methods must be interactive and must be responsive to the multiple demands on these teachers’ time. This requires flexibility in scheduling and course requirements
Quantum Decoherence in a D-Foam Background
Within the general framework of Liouville string theory, we construct a model
for quantum D-brane fluctuations in the space-time background through which
light closed-string states propagate. The model is based on monopole and vortex
defects on the world sheet, which have been discussed previously in a treatment
of 1+1-dimensional black-hole fluctuations in the space-time background, and
makes use of a T-duality transformation to relate formulations with Neumann and
Dirichlet boundary conditions. In accordance with previous general arguments,
we derive an open quantum-mechanical description of this D-brane foam which
embodies momentum and energy conservation and small mean energy fluctuations.
Quantum decoherence effects appear at a rate consistent with previous
estimates.Comment: 16 pages, Latex, two eps figures include
High angular resolution observation of the Sunyaev-Zel'dovich effect in the massive z=0.83 cluster ClJ0152-1357
X-ray observations of galaxy clusters at high redshift (z>0.5) indicate that
they are more morphologically complex and less virialized than those at
low-redshift. We present the first subarcmin resolution at 18 GHz observations
of the Sunyaev-Zel'dovich (SZ) effect for ClJ0152-1357 using the Australia
Telescope Compact Array. ClJ0152-1357 is a massive cluster at redshift z=0.83
and has a complex structure including several merging subclumps which have been
studied at optical, X-ray, and radio wavelengths. Our high-resolution
observations indicate a clear displacement of the maximum SZ effect from the
peak of X-ray emission for the most massive sub-clump. This result shows that
the cluster gas within the cluster substructures is not virialised in
ClJ0152-1357 and we suggest that it is still recovering from a recent merger
event. A similar offset of the SZ effect has been recently seen in the `bullet
cluster' by Malu et al. This non-equilibrium situation implies that high
resolution observations are necessary to investigate galaxy cluster evolution,
and to extract cosmological constraints from a comparison of the SZ effect and
X-ray signals.Comment: 5 pages, 4 figures, submitted to ApJ
Time-Dependent Vacuum Energy Induced by D-Particle Recoil
We consider cosmology in the framework of a `material reference system' of D
particles, including the effects of quantum recoil induced by closed-string
probe particles. We find a time-dependent contribution to the cosmological
vacuum energy, which relaxes to zero as for large times . If
this energy density is dominant, the Universe expands with a scale factor . We show that this possibility is compatible with recent
observational constraints from high-redshift supernovae, and may also respect
other phenomenological bounds on time variation in the vacuum energy imposed by
early cosmology.Comment: 14 pages LATEX, no figure
Exploring positive adjustment in people with spinal cord injury.
This study explored adjustment in people with spinal cord injury; data from four focus groups are presented. Thematic analysis revealed four themes, managing goals and expectations, comparison with others, feeling useful and acceptance, showing participants positively engaged in life, positively interpreted social comparison information and set realistic goals and expectations. These positive strategies show support for adjustment theories, such as the Cognitive Adaptation Theory, the Control Process Theory and Response Shift Theory. These results also provide insight into the adjustment process of a person with spinal cord injury and may be useful in tailoring support during rehabilitation
Image restoration and superresolution as probes of small scale far-IR structure in star forming regions
Far-infrared continuum studies from the Kuiper Airborne Observatory are described that are designed to fully exploit the small-scale spatial information that this facility can provide. This work gives the clearest picture to data on the structure of galactic and extragalactic star forming regions in the far infrared. Work is presently being done with slit scans taken simultaneously at 50 and 100 microns, yielding one-dimensional data. Scans of sources in different directions have been used to get certain information on two dimensional structure. Planned work with linear arrays will allow us to generalize our techniques to two dimensional image restoration. For faint sources, spatial information at the diffraction limit of the telescope is obtained, while for brighter sources, nonlinear deconvolution techniques have allowed us to improve over the diffraction limit by as much as a factor of four. Information on the details of the color temperature distribution is derived as well. This is made possible by the accuracy with which the instrumental point-source profile (PSP) is determined at both wavelengths. While these two PSPs are different, data at different wavelengths can be compared by proper spatial filtering. Considerable effort has been devoted to implementing deconvolution algorithms. Nonlinear deconvolution methods offer the potential of superresolution -- that is, inference of power at spatial frequencies that exceed D lambda. This potential is made possible by the implicit assumption by the algorithm of positivity of the deconvolved data, a universally justifiable constraint for photon processes. We have tested two nonlinear deconvolution algorithms on our data; the Richardson-Lucy (R-L) method and the Maximum Entropy Method (MEM). The limits of image deconvolution techniques for achieving spatial resolution are addressed
An Ultraviolet-Selected Galaxy Redshift Survey - II: The Physical Nature of Star Formation in an Enlarged Sample
We present further spectroscopic observations for a sample of galaxies
selected in the vacuum ultraviolet (UV) at 2000 \AA from the FOCA balloon-borne
imaging camera of Milliard et al. (1992). This work represents an extension of
the initial study of Treyer et al. (1998). Our enlarged catalogue contains 433
sources; 273 of these are galaxies, nearly all with redshifts z=0-0.4. Nebular
emission line measurements are available for 216 galaxies, allowing us to
address issues of reddening and metallicity. The UV and Halpha luminosity
functions strengthen our earlier assertions that the local volume-averaged star
formation rate is higher than indicated from earlier surveys. Moreover,
internally within our sample, we do not find a steep rise in the UV luminosity
density with redshift over 0<z<0.4. Our data is more consistent with a modest
evolutionary trend as suggested by recent redshift survey results. We find no
evidence for a significant number of AGN in our sample. We find the UV flux
indicates a consistently higher mean star formation rate than that implied by
the Halpha luminosity for typical constant or declining star formation
histories. Following Glazebrook et al. (1999), we interpret this discrepancy in
terms of a starburst model for our UV-luminous sources. Whilst we can explain
most of our observations in this way, there remains a small population with
extreme UV-optical colours which cannot be understood.Comment: 27 pages, 19 figures, accepted for publication in MNRA
Cell-free prediction of protein expression costs for growing cells
Translating heterologous proteins places significant burden on host cells, consuming expression resources leading to slower cell growth and productivity. Yet predicting the cost of protein production for any given gene is a major challenge, as multiple processes and factors combine to determine translation efficiency. To enable prediction of the cost of gene expression in bacteria, we describe here a standard cell-free lysate assay that provides a relative measure of resource consumption when a protein coding sequence is expressed. These lysate measurements can then be used with a computational model of translation to predict the in vivo burden placed on growing E. coli cells for a variety of proteins of different functions and lengths. Using this approach, we can predict the burden of expressing multigene operons of different designs and differentiate between the fraction of burden related to gene expression compared to action of a metabolic pathway
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