Debris about asteroids: Where and how much?

We summarize several recent findings on the size and shape of the region within which material can stably orbit an asteroid. If the asteroid (with assumed density 2.38 g/cu cm) circles the Sun at 2.55 AU, co-planar prograde material will remain trapped whenever started on unperturbed circular orbits at less than about 220 R(sub A) (asteroid radii); co-planar retrograde particles are stable out twice as far. Our 3-D stability surface, which encloses several hundred numerically calculated orbits that start with various inclinations, is shaped like a sphere with its top and bottom sliced off; its dimensions scale like the Hill radius =(mu/3)(exp 1/3)R, where mu is the asteroid-to-solar mass ratio and R is the asteroid's orbital radius. If the asteroid moves along an elliptical orbit, a fairly reliable indicator of the dimensions of the hazard zone is the size of its Hill sphere at the orbit's pericenter. Grains with radii less than a few mm will be lost through the action of radiation forces which can induce escape or cause collisions with the asteroid on times scales of a few years; interplanetary micrometeoroids produce collisional break-up of these particles in approximately 10(exp 4) yrs. The effects of Jupiter and of asteroids that pass close to the target asteroid allow particles to diffuse from the system, again shrinking the hazard zone. None of the considered sources-primordial formation, debris spalled off the asteroid during micrometeoroid impact, captured interplanetary particles, feeder satellites, etc., seem capable of densely populating distant orbits from the asteroid. No certain detections of debris clouds or of binary asteroids have been made. Thus, it seems highly unlikely that a spacecraft fly-by targeted at 100 R(sub A) from the asteroid over its orbital pole would encounter any material

A competency-based physical education curriculum for Union Springs Academy

The purpose of the study was to develop a competency-based curriculum for Union Springs Academy, Union Springs, New York. The curriculum was based on the subject areas for which Union Springs Academy had facilities and was in agreement with the philosophy of the Seventh-Day Adventist Church. [This is an excerpt from the abstract. For the complete abstract, please see the document.

Does Corporate Governance Influence Misstatement Disclosure Timeliness?

The relationship between corporate governance and firm disclosure for firms in crisis, specifically firms in violation of GAAP, may differ from the relationship demonstrated in prior literature between governance and voluntary disclosure. An emerging stream of disclosure literature assumes that the relationship between corporate governance and misstatement disclosure choices mirror that found in prior voluntary disclosure literature though no study has empirically demonstrated that a similar relationship exists. Using a sample of 302 accounting irregularities disclosed between 2000 and 2006, I investigate the role of corporate governance, including both internal and external mechanisms, in influencing misstatement disclosure timeliness. I provide empirical evidence consistent with the value of in-the-money stock options incentivizing management to disclose material misstatements in a less timely manner and a non-linear relationship between management ownership and timeliness where lower levels of ownership improve timeliness and higher levels of ownership inhibit timeliness. The results also suggest that greater board independence, CFO turnover prior to the end of the misstated period, and greater risk of civil litigation improve misstatement disclosure timeliness, while greater board size and board classification have the opposite effect

The Tongue River Bison Jump (24RB2135): The Technological Organization of Late Prehistoric Period Hunter-Gatherers in Southeastern Montana

Bison hunting has long been recognized as a key element of the lifeways of American Indians of the Northwestern Plains. Bison served as an integral component for food, shelter, tools, and clothing. It is no surprise that the importance bison hunting, as a socioeconomic institution, is revealed in the archaeological record of this region. A study of the material culture, most often lithic tools, found at prehistoric bison kills and processing sites allows archaeologists to draw inferences about the technology associated with the procurement of such vital animals. An investigation of bison jump, trap or pound lithic assemblage can provide the opportunity to infer the organization of lithic technology associated with communal bison procurement on the Northwestern Plains. The Tongue River Bison Jump (24RB2135) is located in southeastern Rosebud County in southeastern Montana. Due to the low number of previously recorded and tested communal bison procurement sites in the area, investigating this site offered a chance to better understand the social and technological organization of bison procurement in a poorly understood region. This study of the organization of lithic technology is divided into two components: 1) a quantitative typological classification of the tools, and analysis of the debitage; 2) a qualitative comparison of the lithic assemblage with lithic assemblages from other known bison kill sites in a defined geographical study area. The results of this analysis illustrate that the people operating the Tongue River Bison Jump used a generalized biface/core technology to make hunting and butchering tools. Tools reflect an efficient mixture of informal expedient flakes and formalized tools, such as projectile points and scrapers, to complete the task. The tools are predominantly made of porcellanite, a local raw material, but non-local raw materials from as far away as the Big Horn Mountains was observed. This assemblage also may reflect a collector-type social organization where local raw materials were heavily utilized and logistical forays to distant locations where finished tools made of high-quality raw materials were manufactured and transported

The quasi-molecular stage of ternary fission

We developed a three-center phenomenological model,able to explain qualitatively the recently obtained experimental results concerning the quasimolecular stage of a light-particle accompanied fission process. It was derived from the liquid drop model under the assumption that the aligned configuration, with the emitted particle between the light and heavy fragment, is reached by increasing continuously the separation distance, while the radii of the heavy fragment and of the light particle are kept constant. In such a way,a new minimum of a short-lived molecular state appears in the deformation energy at a separation distance very close to the touching point. This minimum allows the existence of a short-lived quasi-molecular state, decaying into the three final fragments.The influence of the shell effects is discussed. The half-lives of some quasimolecular states which could be formed in the $^{10}$Be and $^{12}$C accompanied fission of $^{252}$Cf are roughly estimated to be the order of 1 ns, and 1 ms, respectively