Do Classroom Experiments Affect the Number of Economics Enrollments and Majors?

The present study follows a cohort of 290 students, at an American university, who were exposed to two different pedagogical approaches – traditional 'chalk-and-talk' and classroom experiments. Although we find that the number of majors and upper division economics classes taken were not significantly different between the two groups as a whole, there were some differences across individual characteristics. For example, males who were exposed to classroom experiments enrolled in more upper division economics courses than similar males in the control group. Also, students in the experimental group who had taken economics in high school enrolled in more upper division economics courses than their counterparts in the control group. Minorities in the experimental group, however, enrolled in fewer upper division economics classes than their colleagues in the control group.

Maximum or Minimum Differentiation? An Empirical Investigation into the Location of Firms

We empirically test some implications from location theory using the location of Los Angeles area gasoline stations in physical space and in the space of product attributes. We consider the effect of demand patterns, entry costs, and several proxies for competition -- the total number of stations, the proportion of independent stations, and the proportion of same-brand stations in a market -- on the tendency for a gasoline station to be physically located more or less closely to its competitors. Using an estimation procedure that controls for spatial correlation and controlling for market characteristics as well as non- spatial product attributes, we find that firms locate their stations in an attempt to spatially differentiate their product as general market competition increases. In other words, the incentive to differentiate in order to soften price competition dominates the incentive to cluster locations to attract consumers from rivals. We also find that spatial differentiation increases as stations become more differentiated in other station characteristics.product differentiation, spatial theory, location theory, retail gasoline

Developing Offset Banking Systems in Georgia

Offset banking involves a public or private entity investing in a project that has the effect of substantially reducing a targeted pollutant(s), such as sediment runoff, phosphorus, heavy metals, etc. This project is referred to as "the bank." The entity creating the bank receives "credits" for the associated reduction in pollutants, which it can then sell to publically-owned treatment works (POTWs) or other point source polluters facing high costs of meeting discharge standards. Trades can be allowed on a 1-to-1 basis: the buyer obtains one credit for each creditequivalent increase in pollution associated with his/her activities; or higher trading ratios can be required, e.g., 3:1, where the buyer must acquire (in this example) three credits for each creditequivalent increase in pollution associated with his/her activities. In this latter case trades result in actual environmental improvements.This paper addresses two major issues. The first refers to the steps required to establish a pilot project for one or more offset banking projects in Georgia. These steps are: identifying entities with incentives to purchase offset credits; identifying one or more entities that might establish a bank, and potential bank sites; establishing trading rules with appropriate local water quality management authorities; and obtaining approval of the proposed trading program from the U.S. EPA.The second major issue addressed in the paper is means by which an offset bank might be created. For this purpose, a brief survey is offered of existing water quality trading projects in the U.S.. Buyers of offset credits are virtually always point-source polluters (POTWs or industries). Point and non-point projects have been used as "banks" -- as a source for offset banking credits. Attention in this paper is focused on non-point sources that might serve as banks for pilot offset banking projects in Georgia. Both low- and high-technology alternatives that might be used for such projects are discussed.Notwithstanding incentive-related limitations on the number of point source polluters that might constitute the "demand" for offset credits discussed in section II, the authors have identified one entity (Fulton County) that may represent significant demand for credits, and they expect to identify others. Moreover, the authors argue that continued growth in Georgia, particularly in the Atlanta and Coastal areas of the State, will give rise to sufficient numbers of point source entities seeking new discharge permits to warrant interest in offset banking as a means of meeting increasingly stringent discharge restrictions at minimum cost. If or when enforcement of TMDLs gains strength in the State, needs for systems like offset banking will increase accordingly. These considerations, and the associated benefits to Georgians that might attend the establishment of offset banking programs in the State, serve as the rationale for the author's continued interest in exploring means by which pilot offset banking projects can be established in Georgia. Working Paper # 2003-00

REM Sleep and the emotional brain

Thesis (S.M. in Science Writing)--Massachusetts Institute of Technology, Dept. of Humanities, Graduate Program in Science Writing, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 43-47).Sleep and emotion have been linked since the discovery of rapid eye movement (REM) sleep sixty years ago. Sleep, in particular REM sleep and the dreams it harbors, seems to modulate mood, restoring stability to the weary mind. Scientists have struggled to understand this link through the biological study of the brain, the psychological study of dreaming, and the clinical study of how sleep is affected by psychiatric illness. This thesis examines the history of sleep research in terms of its relationship to emotional processing, both from the physiological and the psychological perspective. We are introduced to the scientists who discovered REM in 1953, to those who tracked the links between the biochemistry of mood and of sleep, and to contemporary researchers who are exploring the link between sleep and mood using brain-scanners and electrodes to study the dreaming brain, and the sleep and dreaming of patients with mood disorders. On our journey we will experience both the progress sleep research has made this century, and the enduring mystery of why humans sleep and dream.by Taylor McGowin Beck.S.M.in Science Writin

Magnetic field structures of galaxies derived from analysis of Faraday rotation measures, and perspectives for the SKA

The forthcoming new-generation radio telescope SKA (Square Kilometre Array) and its precursors will provide a rapidly growing number of polarized radio sources. Our analysis aims on what can be learned from these sources concerning the structure and evolution of magnetic fields of external galaxies. Recognition of magnetic structures is possible from Faraday rotation measures (${\rm RM}$) towards background sources behind galaxies. We construct models for the ionized gas and magnetic field patterns of different azimuthal symmetry (axisymmetric, bisymmetric and quadrisymmetric spiral, and superpositions) plus a halo magnetic field. \RM fluctuations with a Kolmogorov spectrum due to turbulent fields and/or fluctuations in ionized gas density are superimposed. Assuming extrapolated number density counts of polarized sources, we generate a sample of \RM values within the solid angle of the galaxy. Applying various templates, we derive the minimum number of background sources and the minimum quality of the observations. For a large number of sources, reconstruction of the field structure without precognition becomes possible. Any large-scale regular component of the magnetic field can be clearly recognized from \RM data with help of the $\chi^2$ criterium. Under favourite conditions, about a few dozens of polarized sources are sufficient for a reliable result.Comment: 16 pages, 18 figures, accepted for publication in A&

A systematic review to examine the evidence regarding discussions by midwives, with women, around their options for where to give birth

BACKGROUND: Discussion of place of birth is important for women and maternity services, yet the detail, content and delivery of these discussions are unclear. The Birthplace Study found that for low risk, multiparous women, there was no significant difference in neonatal safety outcomes between women giving birth in obstetric units, midwifery-led units, or home. For low risk, nulliparous women giving birth in a midwifery-led unit was as safe as in hospital, whilst birth at home was associated with a small, increased risk of adverse perinatal outcomes. Intervention rates were reduced in all settings outside hospital. NICE guidelines recommend all women are supported in their choice of birth setting. Midwives have the opportunity to provide information to women about where they choose to give birth. However, research suggests women are sometimes unaware of all the options available. This systematic review will establish what is known about midwives’ perspectives of discussions with women about their options for where to give birth and whether any interventions have been implemented to support these discussions. METHODS: The systematic review was PROSPERO registered (registration number: CRD42015017334). The PRISMA statement was followed. Medline, Cochrane, CINAHL, PsycINFO, Popline and EMBASE databases were searched between 2000-March 2015 and grey literature was searched. All identified studies were screened for inclusion. Qualitative data was thematically analysed, whilst quantitative data was summarised. RESULTS: The themes identified relating to influences on midwives’ place of birth discussions with women were organisational pressures and professional norms, inadequate knowledge and confidence of midwives, variation in what midwives told women and the influence of colleagues. None of the interventions identified provided sufficient evidence of effectiveness and were of poor quality. CONCLUSIONS: The review has suggested the need for a pragmatic, understandable place of birth dialogue containing standard content to ensure midwives provide low risk women with adequate information about their place of birth options and the need to improve midwives knowledge about place of birth. A more robust, systematic evaluation of any interventions designed is required to improve the quality of place of birth discussions. By engaging with co-produced research, more effective interventions can be designed, implemented and sustained

The Magnetic Power Spectrum in Faraday Rotation Screens

The autocorrelation function and similarly the Fourier-power spectrum of a rotation measure (RM) map of an extended background radio source can be used to measure components of the magnetic autocorrelation and power-spectrum tensor within a foreground Faraday screen. It is possible to reconstruct the full non-helical part of this tensor in the case of an isotropic magnetic field distribution statistics. The helical part is only accessible with additional information; e.g. the knowledge that the fields are force-free. The magnetic field strength, energy spectrum and autocorrelation length l_B can be obtained from the non-helical part alone. We demonstrate that l_B can differ substantially from l_RM, the observationally easily accessible autocorrelation length of an RM map. In typical astrophysical situation l_RM > l_B. Any RM study, which does not take this distinction into account, likely underestimates the magnetic field strength. For power-law magnetic power spectra, and for patchy magnetic field configurations the central RM autocorrelation function is shown to have characteristic asymptotic shapes. Ways to constrain the volume filling factor of a patchy field distribution are discussed. We discuss strategies to analyse observational data, taking into account - with the help of a window function - the limited extent of the polarised radio source, the spatial distribution of the electron density and average magnetic energy density in the screen, and allowing for noise reducing data weighting. We briefly discuss the effects of possible observational artefacts, and strategies to avoid them.Comment: 15 pages, 4 figures, accepted by Astronomy & Astrophysic

Polarisation properties of Milky-Way-like galaxies

(Abridged) We study the polarisation properties, magnetic field strength, and synchrotron emission scale-height of Milky-Way-like galaxies in comparison with other spiral galaxies. We use our 3D-emission model of the Milky Way Galaxy for viewing the Milky Way from outside at various inclinations as spiral galaxies are observed. When seen edge-on the synchrotron emission from the Milky Way has an exponential scale-height of about 0.74 kpc, which is much smaller than the values obtained from previous models. We find that current analysis methods overestimate the scale-height of synchrotron emission of galaxies by about 10% at an inclination of 80 degree and about 40% at an inclination of 70 degree because of contamination from the disk. The observed RMs for face-on galaxies derived from high-frequency polarisation measurements approximate to the Faraday depths (FDs) when scaled by a factor of two. For edge-on galaxies, the observed RMs are indicative of the orientation of the large-scale magnetic field, but are not well related with the FDs. Assuming energy equipartition between the magnetic field and particles for the Milky Way results in an average magnetic-field strength, which is about two times larger than the intrinsic value for a K factor of 100. The number distribution of the integrated polarisation percentages of a large sample of unresolved Milky-Way-like galaxies peaks at about 4.2% at 4.8 GHz and at about 0.8% at 1.4GHz. Integrated polarisation angles rotated by 90 degree align very well with the position angles of the major axes, implying that unresolved galaxies do not have intrinsic RMs.Comment: 10 pages, 11 figures, accepted for publication in A&