Interim Report of the Meteoroid and Debris Special Investigation Group

The LDEF Meteoroid and Debris Special Investigation Group (hereafter M&D SIG) was formed to maximize the data harvest from LDEF by permitting the characterization of the meteoroid and space debris impact record of the entire satellite. Thus, our work is complementary to that of the various M&D PIs, all of whom are members of the SIG. This presentation will summarize recent results and discussions concerning five critical SIG goals: (1) Classification of impactors based upon composition of residues; (2) Small impact (microimpact) features; (3) Impact cratering and penetration data to derive projectile sizes and masses; (4) Particulate flux estimates in low-Earth orbit; (5) The LDEF Meteoroid and Debris database

Influence of ligand steric bulk in the synthesis of transition-metal borylene complexes

The differing steric requirements of phenyl and mesityl substituents have been shown to influence reactivity in asymmetric transition-metal haloboryl complexes of the type (eta(5)-C5R5)-Fe(CO)(2)B(X)Ar (R = H, Me; X = Cl, Br; Ar = Ph, Mes). Hence substitution of both halides in PhBCl2 can be achieved by reaction with an excess of the bulky organometallic nucleophile Na[(eta(5)-C5Me5)Fe(CO)(2)], to generate [(eta(5)-(CMe5)-Me-5)Fe(CO)](2)(mu-CO)(mu-BPh) (4c), the first metal complex containing the phenylborylene ligand

Fast-Food Government and Physician-Assisted Death: The Role of Direct Democracy in Federalism

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SUMMARY

formed to maximize the data harvest from LDEF by permitting the characterization of the meteoroid and space debris impact record of the entire satellite. Thus, our work is complementary to that of the various M&D PIs, all of whom are members of the SIG. This presentation will summarize recent results and discussions concerning five critical SIG goals: (1) classification of impactors based upon composition of residues, (2) small impact (microimpact) features, (3) impact cratering and penetration data to derive projectile sizes and masses, (4) particulate flux estimates in low-Earth orbit, and (5) the LDEF Meteoroid and Debris database

Interim Report Of The Meteoroid And Debris Special Investigation Group

This report is a first attempt to address these critical issues in a forum accessible to other LDEF investigators and the community at large, both for information purposes and also to invite critique from the larger community. Consensus on these issues has not always been achieved, as will become obvious. However, we are able to delineate the scope of disagreements and suggest ways of resolving them. For example, we recognize that much future work will necessarily concern calibration of craters in aluminum (the most common material on the LDEF), and cratering and penetration processes in the Teflon thermal blankets. As the reader has now discovered, this paper is not a global overview of M&D SIG activities, but is narrowly focussed. We discuss each critical issue below, in the order in which presented above. CRITERIA FOR DISTINGUISHING NATURAL FROM MAN-MADE IMPACTORS Introduction Since different capture experiments on LDEF employed different collection schemes and different analysis techniques, it has proved difficult to establish universal criteria for distinguishing between natural and man-made impactors. The situation becomes more complex for the entire LDEF with its myriad of experimental surfaces and analytical investigations. However, in the interest of promoting the comparisons of results from many laboratories, we propose the following classification scheme. This scheme has been employed for some LDEF studies already (ref. 1). Contamination Clearly, the level and composition of contamination must be carefully established before analysis of residues should be attempted. Also, supposedly well-understood LDEF materials often contain impurities which, though minute on a gross scale, are important at the scale necessary for analysis of impactor residues. LDEF surface..