35 research outputs found
What is a “Just” System for Financing Schools: An Evaluation of Alternative Reforms
Principles for public school finance are outlined with respect to an equitable allocation of educational resources by the state. The argument is advanced that equal dollars per pupil is a practical, reasonable, acceptable and attainable initial basis for school financing. Objections to the equal dollars scheme are considered, leading to an analysis which suggests that the appropriate policy choice for school finance reformers is enactment of full state financing of education
Reactions to Bolon's "Significance of Test-based Ratings for Metropolitan Boston Schools"
Several concerns are raised abut the procedures used and conclusions drawn in Craig Bolon's article "Significance of Test-based Ratings for Metropolitan Boston Schools" published in this journal as Number 42 of Volume 9
Modern Michelson-Morley experiment using cryogenic optical resonators
We report on a new test of Lorentz invariance performed by comparing the
resonance frequencies of two orthogonal cryogenic optical resonators subject to
Earth's rotation over 1 year. For a possible anisotropy of the speed of light
c, we obtain 2.6 +/- 1.7 parts in 10^15. Within the Robertson-Mansouri-Sexl
test theory, this implies an isotropy violation parameter beta - delta - 1/2 of
-2.2 +/- 1.5 parts in 10^9, about three times lower than the best previous
result. Within the general extension of the standard model of particle physics,
we extract limits on 7 parameters at accuracies down to a part in 10^15,
improving the best previous result by about two orders of magnitude
Optical Intensity Interferometry with the Cherenkov Telescope Array
With its unprecedented light-collecting area for night-sky observations, the
Cherenkov Telescope Array (CTA) holds great potential for also optical stellar
astronomy, in particular as a multi-element intensity interferometer for
realizing imaging with sub-milliarcsecond angular resolution. Such an
order-of-magnitude increase of the spatial resolution achieved in optical
astronomy will reveal the surfaces of rotationally flattened stars with
structures in their circumstellar disks and winds, or the gas flows between
close binaries. Image reconstruction is feasible from the second-order
coherence of light, measured as the temporal correlations of arrival times
between photons recorded in different telescopes. This technique (once
pioneered by Hanbury Brown and Twiss) connects telescopes only with electronic
signals and is practically insensitive to atmospheric turbulence and to
imperfections in telescope optics. Detector and telescope requirements are very
similar to those for imaging air Cherenkov observatories, the main difference
being the signal processing (calculating cross correlations between single
camera pixels in pairs of telescopes). Observations of brighter stars are not
limited by sky brightness, permitting efficient CTA use during also bright-Moon
periods. While other concepts have been proposed to realize kilometer-scale
optical interferometers of conventional amplitude (phase-) type, both in space
and on the ground, their complexity places them much further into the future
than CTA, which thus could become the first kilometer-scale optical imager in
astronomy.Comment: Astroparticle Physics, in press; 47 pages, 10 figures, 124 reference
Stellar Intensity Interferometry: Prospects for sub-milliarcsecond optical imaging
Using kilometric arrays of air Cherenkov telescopes, intensity interferometry
may increase the spatial resolution in optical astronomy by an order of
magnitude, enabling images of rapidly rotating stars with structures in their
circumstellar disks and winds, or mapping out patterns of nonradial pulsations
across stellar surfaces. Intensity interferometry (pioneered by Hanbury Brown
and Twiss) connects telescopes only electronically, and is practically
insensitive to atmospheric turbulence and optical imperfections, permitting
observations over long baselines and through large airmasses, also at short
optical wavelengths. The required large telescopes with very fast detectors are
becoming available as arrays of air Cherenkov telescopes, distributed over a
few square km. Digital signal handling enables very many baselines to be
synthesized, while stars are tracked with electronic time delays, thus
synthesizing an optical interferometer in software. Simulated observations
indicate limiting magnitudes around m(v)=8, reaching resolutions ~30
microarcsec in the violet. The signal-to-noise ratio favors high-temperature
sources and emission-line structures, and is independent of the optical
passband, be it a single spectral line or the broad spectral continuum.
Intensity interferometry provides the modulus (but not phase) of any spatial
frequency component of the source image; for this reason image reconstruction
requires phase retrieval techniques, feasible if sufficient coverage of the
interferometric (u,v)-plane is available. Experiments are in progress; test
telescopes have been erected, and trials in connecting large Cherenkov
telescopes have been carried out. This paper reviews this interferometric
method in view of the new possibilities offered by arrays of air Cherenkov
telescopes, and outlines observational programs that should become realistic
already in the rather near future.Comment: New Astronomy Reviews, in press; 101 pages, 11 figures, 185
reference
Four-dimensional String Compactifications with D-Branes, Orientifolds and Fluxes
This review article provides a pedagogical introduction into various classes
of chiral string compactifications to four dimensions with D-branes and fluxes.
The main concern is to provide all necessary technical tools to explicitly
construct four-dimensional orientifold vacua, with the final aim to come as
close as possible to the supersymmetric Standard Model. Furthermore, we outline
the available methods to derive the resulting four-dimensional effective
action. Finally, we summarize recent attempts to address the string vacuum
problem via the statistical approach to D-brane models.Comment: 331 pages, 7 figures, review prepared for Physics Reports, please
send constructive comments to: [email protected], v2: refs added, v3: final
version to appear in Phys. Rep
The PDZ Protein Canoe/AF-6 Links Ras-MAPK, Notch and Wingless/Wnt Signaling Pathways by Directly Interacting with Ras, Notch and Dishevelled
Over the past few years, it has become increasingly apparent that signal transduction pathways are not merely linear cascades; they are organized into complex signaling networks that require high levels of regulation to generate precise and unique cell responses. However, the underlying regulatory mechanisms by which signaling pathways cross-communicate remain poorly understood. Here we show that the Ras-binding protein Canoe (Cno)/AF-6, a PDZ protein normally associated with cellular junctions, is a key modulator of Wingless (Wg)/Wnt, Ras-Mitogen Activated Protein Kinase (MAPK) and Notch (N) signaling pathways cross-communication. Our data show a repressive effect of Cno/AF-6 on these three signaling pathways through physical interactions with Ras, N and the cytoplasmic protein Dishevelled (Dsh), a key Wg effector. We propose a model in which Cno, through those interactions, actively coordinates, at the membrane level, Ras-MAPK, N and Wg signaling pathways during progenitor specification
Pranolium
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/72226/1/j.1527-3466.1983.tb00447.x.pd
3D Head Motion Detection Using Millimeter-Wave Doppler Radar
In advanced driver assistance systems to conditional automation systems, monitoring of driver state is vital for predicting the driver's capacity to supervise or maneuver the vehicle in cases of unexpected road events and to facilitate better in-car services. The paper presents a technique that exploits millimeter-wave Doppler radar for 3D head tracking. Identifying the bistatic and monostatic geometry for antennas to detect rotational vs. translational movements, the authors propose the biscattering angle for computing a distinctive feature set to isolate dynamic movements via class memberships. Through data reduction and joint time-frequency analysis, movement boundaries are marked for creation of a simplified, uncorrelated, and highly separable feature set. The authors report movement-prediction accuracy of 92%. This non-invasive and simplified head tracking has the potential to enhance monitoring of driver state in autonomous vehicles and aid intelligent car assistants in guaranteeing seamless and safe journeys.Peer reviewe