Optimal Addition of Images for Detection and Photometry

In this paper we describe weighting techniques used for the optimal coaddition of CCD frames with differing characteristics. Optimal means maximum signal-to-noise (s/n) for stellar objects. We derive formulae for four applications: 1) object detection via matched filter, 2) object detection identical to DAOFIND, 3) aperture photometry, and 4) ALLSTAR profile-fitting photometry. We have included examples involving 21 frames for which either the sky brightness or image resolution varied by a factor of three. The gains in s/n were modest for most of the examples, except for DAOFIND detection with varying image resolution which exhibited a substantial s/n increase. Even though the only consideration was maximizing s/n, the image resolution was seen to improve for most of the variable resolution examples. Also discussed are empirical fits for the weighting and the availability of the program, WEIGHT, used to generate the weighting for the individual frames. Finally, we include appendices describing the effects of clipping algorithms and a scheme for star/galaxy and cosmic ray/star discrimination.Comment: 27 pages (uuencoded compressed postscript), 199

Contract Structure, Risk Sharing and Investment Choice

Few microfinance-funded businesses grow beyond subsistence entrepreneurship. This paper considers one possible explanation: that the structure of existing microfinance contracts may discourage risky but high-expected return investments. To explore this possibility, I develop a theory that unifies models of investment choice, informal risk sharing, and formal financial contracts. I then test the predictions of this theory using a series of experiments with clients of a large microfinance institution in India. The experiments confirm the theoretical predictions that joint liability creates two inefficiencies. First, borrowers free-ride on their partners, making risky investments without compensating partners for this risk. Second, the addition of peer-monitoring overcompensates, leading to sharp reductions in risk-taking and profitability. Equity-like financing, in which partners share both the benefits and risks of more profitable projects, overcomes both of these inefficiencies and merits further testing in the field.investment choice, informal insurance, risk sharing, contract design, microfinance,experiment.

Improving Transit Predictions of Known Exoplanets with TERMS

Transiting planet discoveries have largely been restricted to the short-period or low-periastron distance regimes due to the bias inherent in the geometric transit probability. Through the refinement of planetary orbital parameters, and hence reducing the size of transit windows, long-period planets become feasible targets for photometric follow-up. Here we describe the TERMS project that is monitoring these host stars at predicted transit times.Comment: 3 pages, 2 figures, to be published in ASP Conf. Proceedings: "Detection and dynamics of transiting exoplanets" 2010, OHP, France (eds.: F. Bouchy, R.F. D{\i}az, C. Moutou

Two-Photon Fluorescence Microscopy for Biomedical Research

This viewgraph presentation gives an overview of two-photon microscopy as it applies to biomedical research. The topics include: 1) Overview; 2) Background; 3) Principles of Operation; 4) Advantages Over Confocal; 5) Modes of Operation; and 6) Applications

Fluid flow within porous media

Includes bibliographical references.The objective of this project is to observe the flow of fluid within a saturated, rectangular, two-dimensional, porous media that is being heated from the side.B.S. (Bachelor of Science

Exoplanet Detection Techniques

We are still in the early days of exoplanet discovery. Astronomers are beginning to model the atmospheres and interiors of exoplanets and have developed a deeper understanding of processes of planet formation and evolution. However, we have yet to map out the full complexity of multi-planet architectures or to detect Earth analogues around nearby stars. Reaching these ambitious goals will require further improvements in instrumentation and new analysis tools. In this chapter, we provide an overview of five observational techniques that are currently employed in the detection of exoplanets: optical and IR Doppler measurements, transit photometry, direct imaging, microlensing, and astrometry. We provide a basic description of how each of these techniques works and discuss forefront developments that will result in new discoveries. We also highlight the observational limitations and synergies of each method and their connections to future space missions.Comment: 24 pages, 19 figures, PPVI proceedings. Appears as 2014, Protostars and Planets VI, Henrik Beuther, Ralf S. Klessen, Cornelis P. Dullemond, and Thomas Henning (eds.), University of Arizona Press, Tucson, 914 pp., p.715-73

Short-term subsidies and seller type: a health products experiment in Uganda

The way in which a product is distributed can have lasting effects on demand by influencing learning, anchoring price expectations, and shaping perceptions of product value. While these issues apply broadly, they are particularly important for health products in poor countries, where short-term subsidies are common, similar products are often available through both non-profit and for-profit organizations, and expanding access is an important public health goal. We implemented a field experiment in northern Uganda in which three curative health products were distributed door-to-door either free or for sale and by either an NGO or for-profit company. For all three products, subsequent purchase rates were lower after a free distribution. While we see no difference in subsequent purchase rates based on seller type, we find that contemporaneous demand for a newly introduced product is higher when the seller identifies as a not-for-profit organization

Nonresponse of native Cottonwood trees to water additions during summer drought

Studies have demonstrated that some riparian trees may switch their reliance on surface soil water (unsaturated or vadose zone) to groundwater (saturated zone) sources during the growing season in association with changes in moisture availability. A closely related question is: How do these trees respond to pulse increases in water availability in previously dry zones? We tested the whole-tree physiological response of 6 natural Populus genotypes to water additions during the peak of summer drought in northern Utah, USA. We found clear evidence that trees were insensitive to water additions to the surface soil that were twice the magnitude of whole-tree transpiration rates. Our results suggest that some cottonwoods may have little immediate transpiration of leaf conductance response to pulse soil moisture increases. This lack of response may be related to water-use strategy associated with regional climate patterns (i.e. genetic or environmental programming), cavitation recovery, or other physical determinants of water use such as depth to groundwater. Our data suggest that it is important to consider potential nonresponsiveness to changes in soil water availability when evaluating the impact of climate change on these important and productive ecosystems