A very long baseline interferometry sky survey

A systematic very long baseline interferometry (VLBI) sky survey, undertaken to find a suitable set of compact celestial radio sources from which a more complete VLBI reference frame can be constructed, discussed. The survey was conducted by searching known celestial radio sources for compact components by means of VLBI observations. Baseline lengths were about 7 x 10 to the 7th power RF wavelengths (lambda = 13.1 cm), so the spatial wavelengths being sampled by the interferometer were generally on the order of a few milliarcseconds. Hence, the radio sources detected have a measurable portion of their total flux density contained in components that are no more than a few milliarcseconds in angular extent. Existing information of radio sources were used as clues to source size

Immigration, wages, and compositional amenities

Economists are often puzzled by the stronger public opposition to immigration than trade, since the two policies have symmetric effects on wages. Unlike trade, however, immigration changes the composition of the local population, imposing potential externalities on natives. While previous studies have focused on fiscal spillovers, a broader class of externalities arise because people value the ‘compositional amenities’ associated with the characteristics of their neighbors and co-workers. In this paper we present a new method for quantifying the relative importance of these amenities in shaping attitudes toward immigration. We use data for 21 countries in the 2002 European Social Survey, which included a series of questions on the economic and social impacts of immigration, as well as on the desirability of increasing or reducing immigrant inflows. We find that individual attitudes toward immigration policy reflect a combination of concerns over conventional economic impacts (i.e., on wages and taxes) and compositional amenities, with substantially more weight on composition effects. Most of the difference in attitudes to immigration between more and less educated natives is attributable to heightened concerns over compositional amenities among the less-educated

An integral equation method for a boundary value problem arising in unsteady water wave problems

In this paper we consider the 2D Dirichlet boundary value problem for Laplace’s equation in a non-locally perturbed half-plane, with data in the space of bounded and continuous functions. We show uniqueness of solution, using standard Phragmen-Lindelof arguments. The main result is to propose a boundary integral equation formulation, to prove equivalence with the boundary value problem, and to show that the integral equation is well posed by applying a recent partial generalisation of the Fredholm alternative in Arens et al [J. Int. Equ. Appl. 15 (2003) pp. 1-35]. This then leads to an existence proof for the boundary value problem. Keywords. Boundary integral equation method, Water waves, Laplace’

Toward an interdisciplinary science of consumption

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/88117/1/j.1749-6632.2011.06163.x.pd

Rigorous theory of nuclear fusion rates in a plasma

Real-time thermal field theory is used to reveal the structure of plasma corrections to nuclear reactions. Previous results are recovered in a fashion that clarifies their nature, and new extensions are made. Brown and Yaffe have introduced the methods of effective quantum field theory into plasma physics. They are used here to treat the interesting limiting case of dilute but very highly charged particles reacting in a dilute, one-component plasma. The highly charged particles are very strongly coupled to this background plasma. The effective field theory proves that this mean field solution plus the one-loop term dominate; higher loop corrections are negligible even though the problem involves strong coupling. Such analytic results for very strong coupling are rarely available, and they can serve as benchmarks for testing computer models.Comment: 4 pages and 2 figures, presented at SCCS 2005, June 20-25, Moscow, Russi

Examining Student Thinking Through Video Analysis

For preservice teachers, videos of children interacting with other children or with teachers can serve as more than a repository of "virtual kids." An inquiry-based approach to watching such video, supported by tools that allow for frequent and close viewing, provides an opportunity for prospective teachers to develop their skills of observation and interpretation before entering the classroom. Furthermore, the in-depth study of videos— particularly if the videos capture situations that reveal something about children's thinking—creates a context in which teachers can act as researchers by gathering evidence, developing hypotheses, and coordinating this information as a guide for further inquiry and teaching. Over time, close and repeated viewing and analysis of video helps shift focus away from the teacher and to the child, and allows for a richer conception of the relationship between children's performance and understanding, to help better inform teaching. Research suggests that a "cognitively rich environment" can aid in the development of the skills of observation, interpretation and argument (Kuhn, 2001a; Kuhn, Shaw, & Felton, 1997). To support teachers' learning about children's thinking, and to help teachers develop these skills, the Columbia Center for New Media Teaching and Learning (CCNMTL) and Prof. Herbert Ginsburg of Teachers College, Columbia University, created a web-based video analysis system called VITAL, or "Video Interactions for Teaching and Learning." The VITAL software is a course management system with tools for enabling students to view, analyze, and write about video. The work preservice teachers perform in VITAL has a number of potential implications for teacher development: first, it grounds learning in the empirical, and second, it offers the opportunity to practice skills of observation, interpretation, and reasoning in preparation for entering the classroom. The immediate goal of the VITAL method is to help preservice teachers (or students from any discipline) become more likely to gather their own evidence of understanding and to encourage them, through repeated viewing and manual interaction with the video content, to be deliberate in validating what they see and in explaining the connections between their evidence and claims about learning. A long-range goal of the method is to help teachers develop a more conditional notion of "the truth" that encourages them to entertain alternative hypotheses and promotes further inquiry and new ideas for teaching. This process represents a recursive, iterative response to new events; gathering more information creates the need for new evidence. By practicing these activities in a controlled setting, teachers can then prepare for classroom-based formative assessment

Mosaic Analysis with Double Markers (MADM) as a Method to Map Cell Fates in Adult Mouse Taste Buds.

Taste buds are chemosensory endorgans embedded in the oral epithelium composed of cells that undergo continuous replacement. Mature taste cells live on average 10-14 days and are replaced by new cells when they die. However, the mechanism by which taste cells are produced and integrated into the taste bud as mature taste cells remains unknown. Previous studies approached this issue from either cell cycle gene expression properties or lineage tracing of precursor cells. In our study, we apply a new fate mapping technique that combines these two ideas. This technique, Mosaic Analysis with Double Markers, allows for simultaneous gene knockout and subsequent tracking of single cells. This allows us to study the potency of precursor cells supplying the taste bud while analyzing how gene function regulates the maturation pathway these taste cells take. The following experiments illustrate the initial phase of this investigation