Large craters on the meteoroid and space debris impact experiment

Examination of 29.37 sq m of thick aluminum plates from the LDEF, which were exposed to the meteoroid and man-made orbital debris environments for 5.8 years, revealed 606 craters that were 0.5 mm in diameter or larger. Most were nearly hemispherical. There was a large variation in the number density of craters around the three axis gravity gradient stabilized spacecraft. A new model of the near-Earth meteoroid environment gives good agreement with the crater fluxes measured on the fourteen faces of the LDEF. The man-made orbital debris model of Kessler, which predicts that 16 pct. of the craters would be caused by man-made debris, is plausible. No chemical analyses of impactor residue that will distinguish between meteoroids and man-made debris is yet available

Meteoroid bumper experiment on Explorer 46

The effectiveness of a meteoroid bumper in reducing meteoroid penetrations is discussed. The bumper reduced the penetration flux by a factor of 30 and demonstrated a weight savings of a factor of 6.9 in the material needed to resist meteoroid penetration. The method of calculating the penetration flux recommended in the NASA space vehicle design criteria for meteoroid damage assessment was found to be very conservative, and changes are suggested. The optimum distribution of material between a bumper and the main wall is discussed

Does small business need a financial fix?

An evaluation of several proposals that would promote additional lending to the small business sector, some through direct government intervention and others by changing existing regulations to promote the market's allocation of credit. The authors argue that market-oriented initiatives are the preferred approach for improving a small-business credit crunch.Small business

More on the differences between reported and actual U.S. central bank foreign exchange intervention

An analysis of the differential impacts of reported and actual U.S. foreign exchange intervention on the mean and conditional variance of the Deutschemark-to-dollar and yen-to-dollar exchange rates. For part of the sample period, the impact of intervention on the variance of the exchange rates is shown to depend on whether the intervention was reported.Foreign exchange - Law and legislation

The inaccuracy of newspaper reports of U.S. foreign exchange intervention

A comparison of official data on U.S. foreign exchange intervention with newspaper reports, finding that the series are systematically different and implying either that intervention may not be able to signal monetary policy accurately or that not all market participants have equally accurate information about exchange market intervention.Foreign exchange - Law and legislation

Catalogue of copepods associated with marine invertebrates at Nosy Bé, Northwestern Madagascar, and vicinity

Dans la région de Nosy Bé, Madagascar, 244 espèces de copépodes s'associent aux 270 espèces d'invertébrés marins, de la zone intertidale jusqu'à une profondeur de 50 mètres. Une liste de ces copépodes avec leurs hôtes et localités est présentée. (Résumé d'auteur

Formative Assessment and Technology in the Mathematics Classroom

This literature review investigates the use of formative assessment and technology in the classroom. There has been research to show that mathematics proficiency has dropped recently in the United States and researchers are looking to identify new strategies for student growth. Utilizing formative assessments, as well as targeted, immediate feedback for students, can help to improve student learning. As educational technology becomes more prevalent, more studies and research are focused around its effectiveness toward student achievement. The research found that formative assessment strategies, coupled with new technologies, can positively impact student achievement