Fiducial Stellar Population Sequences for the u'g'r'i'z' System

We describe an extensive observational project that has obtained high-quality and homogeneous photometry for a number of different Galactic star clusters (including M 92, M 13, M 3, M 71, and NGC 6791) spanning a wide range in metallicity (-2.3<[Fe/H]<+0.4), as observed in the u'g'r'i'z' passbands with the MegaCam wide-field imager on the Canada-France-Hawaii Telescope. By employing these purest of stellar populations, fiducial sequences have been defined from color-magnitude diagrams that extend from the tip of the red-giant branch down to approximately 4 magnitudes below the turnoff: these sequences have been accurately calibrated to the standard u'g'r'i'z' system via a set of secondary photometric standards located within these same clusters. Consequently, they can serve as a valuable set of empirical fiducials for the interpretation of stellar populations data in the u'g'r'i'z' system.Comment: 16 pages, 7 tables, 13 figures; accepted for publication in A

Reflection of P'P' Seismic Waves from Discontinuities in the Mantle

A systematic study of the travel times and apparent velocities of precursors of the seismic core phase PKPPKP indicate that these phases are reflections from the mantle. The strongest reflection is from a depth of 630 km. In order of confidence, other reflectors were found at depths of 280, 520, 940, 410 (very weak), and 1250 km (tentative). The weakness of the 410-km reflection was surprising in view of the large velocity increase at this depth indicated by refraction and Love-wave studies. This transition region must be broader than the others or must involve a smaller density jump. Reflections were observed that were possibly from the top and bottom of the low-velocity zone at depths of 50 and 130 km, respectively. The above reflections are interpreted in terms of the following solid-solid phase changes, in order of increasing depth: pyroxene-garnet solid solution, olivine → β spinel, β spinel → spinel and pyroxene → spinel + stishovite, spinel → post-spinel, and garnet → ilmenite or oxides. A spin-spin transition in Fe^(2+) may be responsible for one of the deeper discontinuities found by others

Validation of the Principal’s High Stakes Testing Survey

The purpose of this study was to examine the soundness of the psychometric characteristics of the Principal’s High Stakes Testing Survey. The 48-item instrument is comprised of six hypothesized subscales (i.e., curriculum, teaching, work satisfaction, stress, accountability, and students) measured with a five-point Likert scale ranging from 1 (strongly disagree) to 5 (strongly agree). An expert panel reviewed the instrument plus an exploratory factor analysis and confirmatory factor analyses were conducted. Expert panel members suggested only a few minor modifications to improve the instrument. The confirmatory factor analyses yielded data to support the fit of the model and the factorial invariance of the model by gender and race or ethnicity

Water And Ice Nucleation Sites From Ion Implantation Of Silicon

Ion implantation has a substantial effect on the heterogeneous nucleation of water and ice. An enhancement of water nucleation and a suppression of ice nucleation occurred for samples of silicon implanted with ions of various species and dosage. These effects were noticeable only for samples implanted with ion doses approaching or exceeding the critical dose necessary to produce amorphous silicon. The behavior of the water droplet and ice crystal growth can be related to the amount of ion produced damage to the substrate surface. The nature of the damage can be controlled by variation of the incident ion species, dose, and energy and thus offers a means of quantifying the surface damage while studying its relationship to heterogeneous nucleation. © 1980 American Chemical Society

Operational Characteristics of Lane Drops

Traffic behavior studies were conducted at seven lane-drop locations, representing three lane-drop classes. These studies consisted of conflict observations (that is, erratic movements and brakelight applications), spot-speed observations, and lane volume counts. Such a study was made before and after each different traffic control device installation in an attempt to determine which device was the most effective in minimizing conflicts at existing lane drops. A study of conflict deviations indicates that no single type of traffic control device studied was significantly effective in reducing erratic movement and brakelight rates at all seven lane-drop locations. Rather, it appears that different traffic control devices are generally most effective at each of the locations. The single-lane exit without taper constituted the lane-drop classification with the lowest conflict rates. Those lane drops with poorer sight geometries were observed to have higher conflict rates. No definitive relationship between traffic conflict rates and either volumes or accident rates was found for the lane drops studied. Certain data limitations were discovered

The Safety Barrier Dilemma

Ran-off-the-road fatal accidents currently account for approximately 65 percent of all freeway fatalities (1). Accordingly, ever-increasing emphasis has been given to the development of effective safety barrier systems, from guardrails to earth berms to median barriers to energy absorbing barriers and mires. However, highway designers have also recognized that safety barriers are hazards in themselves, misfits in the highway environment, and that they are items to be eliminated wherever possible. In a study of fatal accidents on the Interstate Highway System, it was found that fixed object collisions have been the leading source of fatalities, accounting for 43 percent of the 1968-1969 fatal accidents (2). Ironically, guardrails were found to be the most frequent objects struck first -- accounting for 31 percent of the total. Furthermore, this same study estimates that, excluding non-interstate and secondary urban roads, 6,300 miles of guardrail were constructed on public roads in 1969. Statistics such as these illustrate the risks facing today\u27s drivers on the Interstate Highway System. Until a major modification is made that produces a significant reduction in such risks, less mobility (through travel restrictions) will be required to produce a significant reduction in fatalities per year (3)

National Educators' Workshop: Update 1996

This document contains a collection of experiments presented and demonstrated at the National Educators' Workshop: Update 96, held at Los Alamos National Laboratory, Los Alamos, New Mexico on October 27-30, 1996. The experiments related to the nature and properties of engineering materials and provided information to assist in teaching about materials in the education community