The Technology of Public Goods, Externalities, and the Exclusion Principle

Presented here are some notions which we hope will help researchers in their attempts to model various aspects of the complex situations which, currently, come tinder the heading of "externality problems." Roughly, the major theoretical idea is to exploit the advantages of separating into different structural models the consumer-based activities of consumption and acquisition and the producer-based activities of production, marketing, and revenue collection. The links between these activities can then be used to characterize types or classes of externality problems

Dispersal movements of juvenile Black-capped Chickadees

To learn more about Chickadee dispersal this study was undertaken from the summer of 1970 through the summer of 1973, involving the color-banded population of Black-capped Chickadees at the UW-M Cedar-Sauk Field Station described by Weise (1971). The most intensively studied birds were located in about 26 hectares of upland beech-maple forest and about 30 hectares of the cedar-tamarack bog forest at and immediately surrounding the Field Station. The territories of the breeding pairs in these areas were mapped, and as many nests as possible were located. The development of the young in accessible nests was followed, and just before fledging, at an age of about 12 days, the nestlings were color-banded. This involved cutting into the nest cavity, removing the young and banding them, closing the nest cavity, and replacing the young

A Near-Infrared L Band Survey of the Young Embedded Cluster NGC 2024

We present the results of the first sensitive L band (3.4 micron) imaging study of the nearby young embedded cluster NGC 2024. Two separate surveys of the cluster were acquired in order to obtain a census of the circumstellar disk fraction in the cluster. From an analysis of the JHKL colors of all sources in our largest area, we find an infrared excess fraction of > 86%. The JHKL colors suggest that the infrared excesses arise in circumstellar disks, indicating that the majority of the sources which formed in the NGC 2024 cluster are currently surrounded by, and likely formed with circumstellar disks. The excess fractions remain very high, within the errors, even at the faintest L magnitudes from our deeper surveys suggesting that disks form around the majority of the stars in very young clusters such as NGC 2024 independent of mass. From comparison with published JHKL observations of Taurus, we find the K - L excess fraction in NGC 2024 to be consistent with a high initial incidence of circumstellar disks in both NGC 2024 and Taurus. Because NGC 2024 represents a region of much higher stellar density than Taurus, this suggests that disks may form around most of the YSOs in star forming regions independent of environment. We find a relatively constant JHKL excess fraction with increasing cluster radius, indicating that the disk fraction is independent of location in the cluster. In contrast, the JHK excess fraction increases rapidly toward the central region of the cluster, and is most likely due to contamination of the K band measurements by bright nebulosity in the central regions of the cluster. We identify 45 candidate protostellar sources in the central regions of the NGC 2024 cluster, and find a lower limit on the protostellar phase of early stellar evolution of 0.4 - 1.4 X 10^5 yr, similar to that in Taurus.Comment: 37 pages, 8 figures, 3 tables, To appear in the Astronomical Journa

Improved fMRI Time-Series Registration Using Joint Probability Density Priors

Functional MRI (fMRI) time-series studies are plagued by varying degrees of subject head motion. Faithful head motion correction is essential to accurately detect brain activation using statistical analyses of these time-series. Mutual information (MI) based slice-to-volume (SV) registration is used for motion estimation when the rate of change of head position is large. SV registration accounts for head motion between slice acquisitions by estimating an independent rigid transformation for each slice in the time-series. Consequently each MI optimization uses intensity counts from a single time-series slice, making the algorithm susceptible to noise for low complexity endslices (i.e., slices near the top of the head scans). This work focuses on improving the accuracy of MI-based SV registration of end-slices by using joint probability density priors derived from registered high complexity centerslices (i.e., slices near the middle of the head scans). Results show that the use of such priors can significantly improve SV registration accuracy.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/85928/1/Fessler236.pd

U-Pb Ages of Lunar Apatites

Apatite is one of the minerals that is rarely utilized in U-Pb geochronology, compared to some other U-rich accessory phases. Relatively low U concentration, commonly high proportion of common Pb and low closure temperature of U-Pb system of apatite inhibit its application as geochronological tool when other minerals such as zircon are widely available. However, zircon appear to be restricted to certain type of lunar rocks, carrying so called KREEP signature, whereas apatite (and whitlockite) is a common accessory mineral in the lunar samples. Therefore, utilizing apatite for lunar chronology may increase the pool of rocks that are available for U-Pb dating. The low stability of U-Pb systematics of apatite may also result in the resetting of the system during meteoritic bombardment, in which case apatite may provide an additional tool for the study of the impact history of the Moon. In order to investigate these possibilities, we have analysed apatites and zircons from two breccia samples collected during the Apollo 14 mission. Both samples were collected within the Fra Mauro formation, which is interpreted as a material ejected during the impact that formed the Imbrium Basin

A Zircon U-Pb Study of the Evolution of Lunar KREEP

SIMS U-Pb analyses show that zircons from breccias from Apollo 14 and Apollo 17 have essentially identical age distributions in the range 4350 to 4200 Ma but, whereas Apollo 14 zircons additionally show ages from 4200 to 3900 Ma, the Apollo 17 samples have no zircons with ages <4200 Ma. The zircon results also show an uneven distribution with distinct peaks of magmatic activity. In explaining these observations we propose that periodic episodes of KREEP magmatism were generated from a primary reservoir of KREEP magma, which contracted over time towards the centre of Procellarum KREEP terrane