Cryogenic Optical Performance of a Lightweighted Mirror Assembly for Future Space Astronomical Telescopes: Correlating Optical Test Results and Thermal Optical Model

A 43cm diameter stacked core mirror demonstrator was interferometrically tested at room temperature down to 250 degrees Kelvin for thermal deformation. The 2.5m radius of curvature spherical mirror assembly was constructed by low temperature fusing three abrasive waterjet core sections between two CNC pocket milled face sheets. The 93% lightweighted Corning ULE mirror assembly represents the current state of the art for future UV, optical, near IR space telescopes. During the multiple thermal test cycles, test results of interferometric test, thermal IR images of the front face were recorded in order to validate thermal optical model

Cryogenic Optical Performance of a Light-weight Mirror Assembly for Future Space Astronomical Telescopes: Optical Test Results and Thermal Optical Model

A 40 cm diameter mirror assembly was interferometrically tested at room temperature down to 250 degrees Kelvin for thermal deformation. The 2.5 m radius of curvature spherical mirror assembly was constructed by low temperature fusing three abrasive waterjet core sections between two face sheets. The 93% lightweighted Corning ULE mirror assembly represents the current state of the art for future UV, optical, near IR space telescopes. During the multiple thermal test cycles, test results of interferometric test, thermal IR images of the front face were recorded in order to validate thermal optical model

The stories hold water: Learning and burning in North Fork Mono homelands

This essay describes aspects of an eco-cultural restoration program and closely associated educational initiatives and negotiations between the North Fork Mono Tribe and United States governmental agencies. We base our educational approach in Indigenous narrative and land-based experience. We seek not to explain land and water but to help guide students, policymakers, and other learners to come to understand land and water. We consider land, water, plants, and animals as narrators and as sources of knowledge – as primary historical sources, texts that narrate settler colonial and Indigenous history and the physical and cultural changes that colonialism has wrought. As we argue, approaches that combine narratives with visits to the land are key methods in land based education. In addition to describing the theoretical foundations of our curriculum, the essay provides accounts of obstacles presented to us by state education authorities and of successful negotiations to appropriately include tribal knowledge in updates to the California State Water Plan and in agreements with the U.S. Forest Service regarding tribal jurisdictio

Cannabis Dependence and Peer Selection in Social Networks of Frequent Users

In a Dutch longitudinal study on the dynamics of cannabis dependence, at baseline 600 frequent cannabis users (≥ 3 days cannabis use per week in past 12 months) aged 18-30 years were interviewed. Nearly half of all participants (42%) met DSM-IV criteria for cannabis dependence in the 12 months prior to the interview. Participants were recruited by respondent-driven sampling; referrals were understood as proxy for social networks to explore peer associations and social exclusion. Analyses revealed that networks of frequent cannabis users were mostly heterogeneous. Cannabis dependence did not emerge as a main selector. However, within segments of networks some clustering of cannabis dependence (indicating differential inclusion), sex and ethnicity was found. Methodological questions are discussed regarding the applicability of respondent-driven sampling in noninjecting, nonmarginalized drug users. The study’s limitations are noted

Young Adulthood as a Factor in Social Change in the United States

This essay compares family change during two periods of social and historical upheaval in the United States: the industrial revolution of the late nineteenth century and the more recent family changes of the late twentieth century. Despite the manifest social and demographic changes brought about by the industrial revolution, some aspects of family life remained unchanged. Almost all new families formed in the United States before and during the industrial revolution were same-race heterosexual marriages. In the past half-century, however, family diversity has become the new rule; interracial marriages and extramarital cohabitation have both risen sharply. A key to understanding the lack of family diversity in the past and the recent rise in diversity is the changing nature of young adulthood. Copyright 2006 The Population Council, Inc..