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Learning for Adaptation: Building Teacher Career Pathways at DSST Public Schools
The past five years have witnessed unprecedented changes in teacher evaluation systems, as states and districts have responded to federal incentives under the 2009 Race to the Top grant competition. Across the country, teacher evaluation has become more frequent, higher stakes, and more explicitly tied to student achievement outcomes. This capstone examines the initial implementation of one such system at DSST Public Schools, a network of nine consistently high-performing charter schools in Denver, Colorado. I describe my role in leading a cross-functional team charged with implementing, learning from, and improving the system in its first full year. I explore the everyday challenges of positioning evaluation as a resource to drive teacher development, arguing that evaluation will achieve lofty developmental goals only if teams of system designers and system users decouple the measurement and development purposes of teacher evaluation and commit to the creation of complementary systems. Leaders can accelerate this process by modeling a developmental mindset and creating conditions for purposeful team learning that leads to system adaptation. This capstone offers important lessons for practitioners and policymakers seeking to position teacher evaluation as a resource for teacher growth and development; for DSST Public Schools in its effort to develop teachers and leaders across its expanding network of schools; and for myself as an educational leader
The Impact of Personal Experience on Behavior: Evidence From Video-Rental Fines
Personal experience matters. In a field setting with longitudinal data, we disentangle the effects of learning new information from the effects of personal experience. We demonstrate that experience with a fine, controlling for the effect of learning new information, significantly boosts future compliance. We also show that experience with a large fine boosts compliance more than experience with a small fine, but that the influence of experience with both large and small fines decays sharply over time
Aspherical Explosion Models for SN 1998bw/GRB 980425
The recent discovery of the unusual supernova SN1998bw and its apparent
correlation with the gamma-ray burst GRB 980425 has raised new issues
concerning both the GRB and supernovae. Although the spectra resemble those of
TypeIc supernovae, there are distinct differences at early times and SN1998bw
appeared to be unusually bright and red at maximum light. The apparent
expansion velocities inferred by the Doppler shift of (unidentified) absorption
features appeared to be high, making SN1998bw a possible candidate for a
"hypernova" with explosion energies between 20 and 50E51 erg and ejecta masses
in excess of 6 - 15 M_o. Based on light curve calculations for aspherical
explosions and guided by the polarization observations of "normal" SNIc and
related events, we present an alternative picture that allows SN1998bw to have
an explosion energy and ejecta mass consistent with core collapse supernovae
(although at the 'bright' end). We show that the LC of SN1998bw can be
understood as result of an aspherical explosion along the rotational axis of a
basically spherical, non-degenerate C/O core of massive star with an explosion
energy of 2foe and a total ejecta mass of 2 M_o if it is seen from high
inclinations with respect to the plane of symmetry. In this model, the high
expansion velocities are a direct consequence of an aspherical explosion which,
in turn, produces oblate iso-density contours. It suggests that the fundamental
core-collapse explosion process itself is strongly asymmetric.Comment: 12 pages, 8 figures, latex, aas2pp4.sty, submitted to Ap
Discovery of a New Soft Gamma Repeater, SGR 1627-41
We report the discovery of a new soft gamma repeater (SGR), SGR 1627-41, and
present BATSE observations of the burst emission and BeppoSAX NFI observations
of the probable persistent X-ray counterpart to this SGR. All but one burst
spectrum are well fit by an optically thin thermal bremsstrahlung (OTTB) model
with kT values between 25 and 35 keV. The spectrum of the X-ray counterpart,
SAX J1635.8-4736, is similar to that of other persistent SGR X-ray
counterparts. We find weak evidence for a periodic signal at 6.41 s in the
light curve for this source. Like other SGRs, this source appears to be
associated with a young supernova remnant G337.0-0.1. Based upon the peak
luminosities of bursts observed from this SGR, we find a lower limit on the
dipole magnetic field of the neutron star B_dipole > 5 * 10^14 Gauss.Comment: 5 pages, 4 figures, submitted to ApJ Letter
Detailed Analysis of the Pulsations During and After Bursts from the Bursting Pulsar (GRO J1744-28)
The hard X-ray bursts observed during both major outbursts of the Bursting
Pulsar (GRO J1744-28) show pulsations near the neutron star spin frequency with
an enhanced amplitude relative to that of the persistent emission. Consistent
with previous work, we find that the pulsations within bursts lag behind their
expected arrival times based upon the persistent pulsar ephemeris. For an
ensemble of 1293 bursts recorded with the Burst and Transient Source
Experiment, the average burst pulse time delay is 61.0 +/- 0.8 ms in the 25 -
50 keV energy range and 72 +/- 5 ms in the 50 - 100 keV band. The residual time
delay from 10 to 240 s following the start of the burst is 18.1 +/- 0.7 ms (25
- 50 keV). A significant correlation of the average burst time delay with burst
peak flux is found. Our results are consistent with the model of the pulse time
lags presented by Miller (1996).Comment: 11 pages, accepted for publication in Ap
The Dynamic Behavior of Soft Gamma Repeaters
Soft Gamma Repeaters (SGRs) undergo changes in their pulse properties and
persistent emission during episodes of intense burst activity. Both SGR 1900+14
and SGR 1806-20 have shown significant changes in their spin-down rates during
the last several years, yet the bulk of this variability is not correlated with
burst activity. SGR 1900+14 has undergone large changes in flux and a dramatic
pulse profile change following burst activity in 1998. The flux level of SGR
162741 has been decreasing since its only recorded burst activity. Here, we
review the global properties of SGRs as well as the observed dynamics of the
pulsed and persistent emission properties of SGR 1900+14, SGR 1806-20 and SGR
1627-41 during and following burst active episodes and discuss what
implications these results have for the burst emission mechanism, the magnetic
field dynamics of magnetars, the nature of the torque variability, and SGRs in
general.Comment: Invited review to appear in "High Energy Studies of Supernova
Remnants and Neutron Stars" (COSPAR 2002). 12 pages, 7 figure
5-10 GeV Neutrinos from Gamma-Ray Burst Fireballs
A gamma-ray burst fireball is likely to contain an admixture of neutrons, in
addition to protons, in essentially all progenitor scenarios. Inelastic
collisions between differentially streaming protons and neutrons in the
fireball produce muon neutrinos (antineutrinos) of ~ 10 GeV as well as electron
neutrinos (antineutrinos) of ~ 5 GeV, which could produce ~ 7 events/year in
kilometer cube detectors, if the neutron abundance is comparable to that of
protons. Photons of ~ 10 GeV from pi-zero decay and ~ 100 MeV electron
antineutrinos from neutron decay are also produced, but will be difficult to
detect. Photons with energies < 1 MeV from shocks following neutron decay
produce a characteristic signal which may be distinguishable from the
proton-related MeV photons.Comment: 4 pages, latex, 1 figure, aps style files. Final version, accepted in
Phys.Rev.Lett., 6/22/2000; some clarifications in the text, same conclusion
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