The Optical/Infrared Astronomical Quality of High Atacama Sites. II. Infrared Characteristics

We discuss properties of the atmospheric water vapor above the high Andean plateau region known as the Llano de Chajnantor, in the Atacama Desert of northern Chile. A combination of radiometric and radiosonde measurements indicate that the median column of precipitable water vapor (PWV) above the plateau at an elevation of 5000 m is approximately 1.2 mm. The exponential scaleheight of the water vapor density in the median Chajnantor atmosphere is 1.13 km; the median PWV is 0.5 mm above an elevation of 5750 m. Both of these numbers appear to be lower at night. Annual, diurnal and other dependences of PWV and its scaleheight are discussed, as well as the occurrence of temperature inversion layers below the elevation of peaks surrounding the plateau. We estimate the background for infrared observations and sensitivities for broad band and high resolution spectroscopy. The results suggest that exceptional atmospheric conditions are present in the region, yielding high infrared transparency and high sensitivity for future ground-based infrared telescopes.Comment: 25 pages, 11 figures, to appear in the PASP (July 2001

First Science Observations with SOFIA/FORCAST: Properties of Intermediate-Luminosity Protostars and Circumstellar Disks in OMC-2

We examine eight young stellar objects in the OMC-2 star forming region based on observations from the SOFIA/FORCAST early science phase, the Spitzer Space Telescope, the Herschel Space Observatory, 2MASS, APEX, and other results in the literature. We show the spectral energy distributions of these objects from near-infrared to millimeter wavelengths, and compare the SEDs with those of sheet collapse models of protostars and circumstellar disks. Four of the objects can be modelled as protostars with infalling envelopes, two as young stars surrounded by disks, and the remaining two objects have double-peaked SEDs. We model the double-peaked sources as binaries containing a young star with a disk and a protostar. The six most luminous sources are found in a dense group within a 0.15 x 0.25 pc region; these sources have luminosities ranging from 300 L_sun to 20 L_sun. The most embedded source (OMC-2 FIR 4) can be fit by a class 0 protostar model having a luminosity of ~50 L_sun and mass infall rate of ~10^-4 solar masses per year.Comment: Accepted by ApJ Letter

Assessing the mechanisms of common Pb incorporation into titanite

Common Pb, the portion of non-radiogenic Pb within a U bearing mineral, needs to be accurately accounted for in order to subtract its effect on U-Pb isotopic ratios so that meaningful ages can be calculated. The propensity to accommodate common Pb during crystallization, or later, is different across the range of U bearing minerals used for geochronology. Titanite frequently accommodates significant amounts of common Pb. However, the most appropriate method to correct for this requires knowledge on the mechanism and timing of common Pb incorporation; information that is commonly difficult to extract. In this study, the spatial and compositional distribution of trace elements (including Pb) in metamorphic titanites from a Greenland amphibolite is investigated on the grain- to nano-scale. Titanites have an isotopically similar signature for both common and radiogenic-Pb in all grains but significantly different quantities of the non-radiogenic component. Microstructural and compositional examination of these grains reveals undeformed, but high common Pb (F207%) titanites have homogeneous element distributions on the atomic scale suggesting common Pb is incorporated into titanite during its growth and not during later processes. In contrast, deformed titanite comprising low-angle boundaries, formed by subgrain rotation recrystallization, comprise networks of dislocations that are enriched in Mg, Al, K and Fe. Smaller cations may migrate due to elastic strain in the vicinity of the dislocation network, yet the larger K cations more likely reflect the mobility of externally-derived K along the orien tation interface. The absence of Pb enrichment along the boundary indicates that either Pb was too large to fit into migrating lattice dislocations or static low-angle boundaries and/or that there was no external Pb available to diffuse along the grain boundary. As the common Pb composition is distinctly different to regional Pb models, the metamorphic titanite grew in a homogeneous Pb reservoir dominated by the break-down of precursor U-bearing phases. The different quantity of common Pb in the titanite grains indicates a mineral-driven element partitioning in an isotopically homogeneous metamorphic reservoir, consistent with low U, low total REE and flat LREE signatures in high F207% analyses. These results have implications for the selection of appropriate common Pb corrections in titanite and other accessory phases

Surface Chemistry of Perfluoropolyethers and Hydrogenated Analogs: Are Studies of Model Compounds Useful?

We have studied adsorption, desorption, and decomposition of ethers on Ru(001), an atomically-smooth metal surface. We have compared diethers with monoethers, and fluorinated ethers with hydrogenated ethers. The number of ether linkages does not strongly influence adsorption bond strength, nor the extent of decomposition. Fluorination does weaken the adsorption bond strength and prevents decomposition. These studies suggest that the surface properties of monomeric ethers can be used to predict properties of oligomeric, and perhaps even polymeric, ethers

Implementation of the Power to Prevent Diabetes Prevention Educational Curriculum Into Rural African American Communities: A Feasibility Study

The purpose of this study was to describe the feasibility of using a Community Based Participatory Research (CBPR) approach to implement the Power to Prevent (P2P) diabetes prevention education curriculum in rural African American (AA) settings

Externalising tacit overview knowledge: A model-based approach to supporting design teams

Successful realization of large-scale product development programs is challenging because of complex product and process dependencies and complicated team interactions. Proficient teamwork is underpinned by knowledge of the manner in which tasks performed by different design participants fit together to create an effective whole. Based on an extensive industrial case study with a diesel engine company, this paper first argues that the overview and experience of senior designers play an important part in supporting teamwork by coordinating activities and facilitating proactive communication across large project teams. As experts move on and novices or contractors are hired, problems are likely to occur as tacit overview knowledge is lost. If informal, overview-driven processes break down, the risk of costly oversights will increase, and greater management overhead will be required to realize successful product designs. Existing process models provide a means to express the connectivity between tasks and components thus to compensate partially for the loss of tacit overview. This paper proposes the use of design confidence, a metric that reflects the designer's belief in the maturity of a particular design parameter at a given point in the process, to address the limitations of existing models. The applicability of confidence-based design models in providing overview, as well as their shortcomings, will be demonstrated through the example of a diesel engine design process. Confidence can be used to make overview knowledge explicit and convey additional information about the design artifact, thereby informing communication and negotiation between team

Gene-body hypermethylation of ATM in peripheral blood DNA of bilateral breast cancer patients

Bilaterality of breast cancer is an indicator of constitutional cancer susceptibility; however, the molecular causes underlying this predisposition in the majority of cases is not known. We hypothesize that epigenetic misregulation of cancer-related genes could partially account for this predisposition. We have performed methylation microarray analysis of peripheral blood DNA from 14 women with bilateral breast cancer compared with 14 unaffected matched controls throughout 17 candidate breast cancer susceptibility genes including BRCA1, BRCA2, CHEK2, ATM, ESR1, SFN, CDKN2A, TP53, GSTP1, CDH1, CDH13, HIC1, PGR, SFRP1, MLH1, RARB and HSD17B4. We show that the majority of methylation variability is associated with intragenic repetitive elements. Detailed validation of the tiled region around ATM was performed by bisulphite modification and pyrosequencing of the same samples and in a second set of peripheral blood DNA from 190 bilateral breast cancer patients compared with 190 controls. We show significant hypermethylation of one intragenic repetitive element in breast cancer cases compared with controls (P = 0.0017), with the highest quartile of methylation associated with a 3-fold increased risk of breast cancer (OR 3.20, 95% CI 1.78–5.86, P = 0.000083). Increased methylation of this locus is associated with lower steady-state ATM mRNA level and correlates with age of cancer patients but not controls, suggesting a combined age–phenotype-related association. This research demonstrates the potential for gene-body epigenetic misregulation of ATM and other cancer-related genes in peripheral blood DNA that may be useful as a novel marker to estimate breast cancer risk

Studying Genetic Research Participants: Lessons from the "Learning About Research in North Carolina" Study

Given the prohibitive cost of recruiting large and diverse populations for genetic explorations in cancer research, there has been a call for genetic studies to engage existing cohorts of research participants. This strategy could lead to more efficient recruitment and potentially result in significant advances in the understanding of cancer etiology and treatment. The Learning About Research in North Carolina (LeARN) study responded to the National Human Genome Research Institute interest in research on how study participants from diverse populations who had participated in genetic research perceived the risks and benefits of participating in combined epidemiologic-genetic research, how well they understand the purpose of the research and the uses to which the research results may be put, and how involvement in such research affects perceptions of disease causality. In this paper we give an overview of the LeARN study, summarizing the methods we used, challenges we encountered, and lessons learned about recruiting participants who have previously participated in genetic research