A proof-of-principle experiment has been carried out in the Final Focus Test Beam (FFTB) at SLAC to demonstrate production of polarized positrons in a manner suitable for implementation at the ILC. A ...helical undulator of 2.54 mm period and 1-m length produced circularly polarized photons of first harmonic endpoint energy of 8 MeV when traversed by a 46.6 GeV electron beam. The polarized photons were converted to polarized positrons in a 0.2-radiation-length tungsten target. The polarization of these positrons was measured at several energies, with a peak value in excess of 80%, by transmission polarimetry of photons obtained on reconversion of the positrons in a second tungsten target.
The goal of this study was to develop a primary culture model of differentiated murine tracheal epithelium. When grown on semipermeable membranes at an air interface, dissociated murine tracheal ...epithelial cells formed confluent polarized epithelia with high transepithelial resistances (tilde12 kOmega - cm2) that remained viable for up to 80 days.
Thesis (Ed. D.)--Texas A&M University, 2007.
"Major Subject: Educational Administration" Title from author supplied metadata (automated record created on Nov. 2, 2007.) Vita. Abstract. Includes ...bibliographical references.
This study, one of four cohort studies, was designed to determine the relationship
between student performance and leadership practices as perceived by principals and
selected site-based decision ...making committee members of middle schools in the
Region 5 Education Service Center area of Texas. Using the Leadership Practices
Inventory developed by Kouzes and Posner, the study compared the perceptions of
middle school principals and selected observers regarding leadership practices. These
leadership ratings were compared to student achievement for each campus in the
study. In addition, the study examined if selected demographic variables impact the
perception of leaders and observers in regard to leadership.
For schools in this particular study, there was no direct correlation between
perceived leadership practices of the principals and student achievement as measured
by the Texas Assessment of Knowledge and Skills (TAKS) tests. This was true of
total LPI scores and also of each individual practice measured by the LPI. The data revealed that principals in the study rated themselves higher as a group
than their observers rated them on the LPI. This trend was consistent for the total
instrument and for each leadership practice. There were also similarities, however,
between the two groups. The practice Model the Way had the highest mean for both
groups, while Inspire a Shared Vision and Enable Others to Act were rated lower by
both groups of respondents.
A researcher-developed questionnaire was used to gather demographic information
about each respondent. Years of experience, age group, gender, and ethnicity
were all studied to determine if they had any effect on responses. The results indicate
that there were some differences when principals and observers were studied separately,
but these differences were minimized when the two groups were combined.
Of particular interest was the fact that younger principals and less experienced
principals rated themselves more conservatively than their older and more
experienced colleagues. Younger observers and less experienced observers, however,
had a propensity to rate their leader high when compared to older observers and more
experienced observers. Neither ethnicity nor gender had an impact on leader ratings.
Precipitation and runoff records from several burned watersheds have been used to evaluate the performance of the Automated Geospatial Watershed Assessment (AGWA) tool as it is used to assign ...parameters to the KINmatic runoff and EROSion Model 2 (KINEROS2). This modeling scheme is used by the Department of Interior Burned Area Emergency Response (DOI BAER) teams to assess flooding and erosion risk immediately following a wildfire. Although DOI BAER teams use this parameterization/modeling framework to assess the relative change in watershed behavior following a wildfire by driving the model with National Oceanic and Atmospheric Administration (NOAA) design storms, calibrations performed on actual events using rainfall estimations provided by rain gages and radar to drive the model provides insight into the model's performance, and potentially informs changes and developments to the AGWA parameter estimation scheme. Results indicate that current parameter modifications made by AGWA to represent fire impacts provide reasonable results for DOI BAER relative change risk assessments, though additional modifications to saturated hydraulic conductivity may be necessary to represent a broader range of storm intensity.
On 15 February 2013, the asteroid 367943 Duende (2012 DA14) experienced a near-Earth encounter at an altitude of 27,700 km or 4.2 Earth radii. We present here the results of an extensive, ...multi-observatory campaign designed to probe for spectral and/or rotational changes to Duende due to gravitational interactions with the Earth during the flyby. Our spectral data reveal no changes within the systematic uncertainties of the data. Post-flyby lightcurve photometry places strong constraints on the rotation state of Duende, showing that it is in non-principal axis rotation with fundamental periods of P_1 = 8.71 +/- 0.03 and P_2 = 23.7 +/- 0.2 hours. Multiple lightcurve analysis techniques, coupled with theoretical considerations and delay-doppler radar imaging, allows us to assign these periods to specific rotational axes of the body. In particular we suggest that Duende is now in a non-principal, short axis mode rotation state with a precessional period equal to P_1 and oscillation about the symmetry axis at a rate equal to P_2. Temporal and signal-to-noise limitations inherent to the pre-flyby photometric dataset make it difficult to definitively diagnose whether these periods represent a change imparted due to gravitational torques during the flyby. However, based on multiple analysis techniques and a number of plausibility arguments, we suggest that Duende experienced a rotational change during the planetary encounter with an increase in its precessional rotation period. Our preferred interpretation of the available data is that the precession rate increased from 8.4 hours prior to the flyby to 8.7 hours afterwards. A companion paper by Benson et al. (2019) provides a more detailed dynamical analysis of this event and compares the data to synthetic lightcurves computed from a simple shape model of Duende. (abbreviated abstract)
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